Also, what is the percentage of True Bugs compared to the insect population?
I'm writing a children's book on bugs and I'm comparing the true bug to the insect. All population info seems to combine the two. Please list sources.
What is the percentage of true bugs compared to all animal species on the plant? - Biology
The Orthotylinae and Phylinae (Insecta: Heteroptera: Miridae) are world-wide groups currently containing
4000 highly host-specific phytophagous species (Fig. 1). They comprise about 40 percent of all described species of the plant bug family Miridae , one of the most speciose lineages of non-holometabolous insects. Arguments for the monophyly of the Orthotylinae and Phylinae have been made on the basis of female genitalia (Slater, 1950), male genitalia (Kelton, 1959 Kerzhner and Konstantinov, 1999), and scent-gland morphology (Cassis, 1995), and from a total evidence perspective (Schuh, 1974, 1976). The monophyly of the two subfamilies is corroborated by preliminary analyses of a partial set of the DNA sequence data for 115 species representing 63 genera collected by Wheeler and Schuh under NSF grant DEB-9726587 (see Results of Prior Support). Arguments for sister-group status of the two taxa have also been made (Reuter, 1905 Wagner, 1955 Leston, 1961 Schuh, 1974, 1976).
Comparison of the current classification of the Orthotylinae and Phylinae (Schuh, 1995 http://research.amnh.org/invertzoo/miridae/ Cassis and Gross, 1995) with the baseline work of Carvalho (1952, 1957-1960) indicates significant changes over the last 3 decades (compare Figs. 2 and 3). In the classification of Carvalho (1952) the Phylinae were diagnosed by a plesio-morphic character (setiform parempodia) widely distributed in the Miridae and other Heteroptera, with the consequent inclusion of Dicyphini, a group now placed outside the orthotyline-phyline clade. Also, Carvalho placed the Pilophorini in the subfamily Orthotylinae, solely on the basis of pretarsal structure, an action that Schuh (1974, 1976, 1991), Cassis (1995), and Kerzhner and Konstantinov (1999) have argued is unsupported by other character data. Moreover, because of his very literal interpretation of parempodial structure, Carvalho misplaced a large number of genera, most of them being Phylinae interpreted as Orthotylinae. Lastly, Carvalho diagnosed several tribes on the basis of myrmecomorphic habitus, a "character" that was ill defined, subject to interpretation, and often conflicted with other characters. Many of these "flaws" in Carvalho's classification were addressed by Schuh (1974, 1984, 1991) and Cassis (1995). The higher classification of the subfamilies is now more stable than was that of Carvalho, with most suprageneric taxa being diagnosed on the basis of apomorphic characters.
Significant knowledge of phylogenetic relationships has also been developed below the tribal level. Schuh (1984) prepared a generic-level phylogeny for the tribes Auricillocorini and Leucophoropterini in the Indo-Pacific and for world Pilophorini (Schuh, 1991). Phylogenetic relationships of generic groups in other tribes have been studied by Stonedahl and Schuh (1986), Henry (1991), and Cassis and Asquith (submitted), among others. Species-level phylogenies exist for such complex genera as Pseudopsallus Van Duzee (Schwartz and Stonedahl, 1986 Stonedahl and Schwartz, 1986, 1988) Atractotomus Fieber (Stonedahl, 1990), and Kirkaldyella Poppius (Cassis and Moulds, 2002), among others.
State of Descriptive Taxonomy
The accumulation of described species over time, by classic biogeographic region, can be seen in Fig. 4. Clearly much of the descriptive work in all regions has occurred in the last 3 decades. Possibly the most remarkable feature of these data is that only a tiny part of the described world fauna is from Australia. The figure further suggests that the fauna of all southern continents is depauperate compared to that of the Holarctic, a subject we will address in detail.
Fig. 2. Carvalho (1952, 1958) Fig. 3. Schuh (1974, 1976, 1984)
Information for Australia indicates that the low species numbers for that region are artificial. For example, as of 1995 CoPI Cassis had borrowed most collections of Australian Miridae to assess the state of taxonomy for the group in the region. These collections contained
5000 were Orthotylinae and Phylinae, and nearly half of those comprised a few species commonly collected on crop or ruderal plants
1000 species of Miridae were represented. Thus, the 180 described species listed by Cassis and Gross (1995) appears to be an abysmal indicator of actual diversity in the Australian Miridae, based on this data source.
PIs Cassis and Schuh began a series of expeditions in 1995 to improve the sample of Australian Miridae. Their efforts have yielded >75,000 specimens from >400 localities (see Fig. 6), most being members of the Orthotylinae and Phylinae. At least 95% of all specimens collected by Cassis and Schuh have documented hosts, 1205 plant vouchers having been identified. Fig. 5 shows the numbers of species of bugs per host, indicating that the sample of Orthotylinae and Phylinae so far collected probably exceeds 1400 species, a very large percentage of which were not present among the
1000 species found in the pre-existing collections mentioned above. Cassis and Moulds (2002) described in the orthotyline genus Kirkaldyella Poppius 14 species as new from the 15 total that they listed for this Australian group most specimens came from fieldwork of Cassis and Schuh.
Fig. 4. Accumulation of described species of Orthotylinae and Phylinae over time by continental region.
Fig. 5. Count of Australian mirid species by host plant (based on Cassis/Schuh host data).
The sample of Australian Miridae now available for study is immensely greater than what existed 7 years ago. Yet, we believe it still undersamples the fauna because the number of host species recorded underrepresents the total flora, and because the areas sampled by Cassis and Schuh still leave some parts of the continent untouched, as can be seen in Fig. 6. This PBI project offers the opportunity to improve that sample and to describe the fauna comprehensively as part of a larger global study.
Undersampling of the Australian fauna can be further judged by noting that approximately 18,000 species of flowering plants occur in Australia (Costermans, 1994), roughly twice the number found in North America north of Mexico. Within Australia, approximately 3200 plant species occur only in the far southwest (Corrick and Fuhrer, 1996), a region which comprises about 2% of the land area of the continent and is a Mediterranean hotspot. Yet, there are more than 2000 valid species of Miridae known from North America compared to the fewer than 200 recorded for all of Australia (Henry and Wheeler, 1988 Cassis and Gross, 1995 Schuh, 1995). Even a rough correlation between plant bug and plant diversity would predict in excess of 2000 species of Australian Miridae. Data in Fig. 5 suggest that this is almost certainly the case.
Fig. 6. Australian localities sampled for Miridae by Cassis and Schuh, 1995-2001
A second graphic example of undersampling for the southern fauna is provided by southern Africa, an area with > 23,000 plant species. The Cape Floristic region (fynbos biome) occupies 3.5% of the land area in southern Africa but contains 41% of the plant species, ranking its as one of the botanically most species-rich areas in the world (Cowling and Hilton-Taylor, 1994 Low and Robelo, 1996). Yet, the total numbers of species of Miridae, and more particularly Orthotylinae and Phylinae, currently known from southern Africa is small compared with total plant diversity. Trends of species description suggest that a tremendous amount of diversity remains to be discovered and described. For example, Carvalho et al. (1960) listed 12 species in 12 genera, based solely on the collections of the Lund University Expeditions from the early 1950s. Schuh (1974), who examined a broader range of collections, documented 103 species in 54 genera of Orthotylinae and Phylinae, 81 of the species and 20 of the genera being described as new. A small fraction of the material examined by Schuh was from the far south-west, and virtually none of it was collected during the crucial months of September-November. The remainder of the Ethiopian fauna has been documented in substantial detail, primarily through the works of Linnavuori (e.g., Linnavuori, 1975, 1993, 1994).
Finally, Chile and Argentina are known for their southern biotic connections. PI Schuh conducted field work in the region on 3 separate occasions. Examination of the literature and existing collections indicates that the fauna of the region is not nearly so diverse as those of Australia and southern Africa, but that it is nonetheless crucial from a phylogenetic perspective because of possible biogeographic connections to New Zealand. We have budgeted for additional fieldwork in the region to potentially improve our sample of taxa. The fauna of tropical areas of the Neotropical region has been documented in a very large number of papers by the late J.C.M. Carvalho (see Schuh, 1995). Senior Investigator T. J. Henry has done extensive field work in southern Brazil. These efforts show the Orthotylinae to be much more diverse than the Phylinae, and indicate that significant descriptive work remains to be done (see Table 2).
In summary, although species diversity in the Holarctic appears to be much greater than on the southern continents, the reality appears to be that these fragments of Gondwana are just inadequately studied. Thus, a focal point of this proposal is to collect, document, and describe the southern fauna as part of our effort to monograph the Orthotylinae and Phylinae for the World.
Current Knowledge of Biology, Biogeography, and Biodiversity: Broader Impacts and Non-Systematic Conceptual Issues Biological Information
Host Associations and Specificity: In an effort to assemble information on patterns of host association in the Miridae, Schuh (1995) included
2800 species of Miridae. The updated web-based catalog of Miridae, on which Figs. 7 and 8 are based, provides a substantial increase in the number of hosts, with a total of
6200 host records for a total of 3044 species of Miridae, of which
1750 are species of Orthotylinae and Phylinae.
The histograms in Figs. 7 and 8 reveal two strongly supported patterns of host association, based on data for about 30% of described mirid species. First, although most known plant hosts harbor a single mirid species, a significant number of plants serve as hosts for multiple bug species. Second, a preponderance of mirid species appear to be host specific. The 1205 hosts documented by PIs Cassis and Schuh for Australia (see Fig. 5) also portray these patterns.
Host data for the Miridae are collected as a direct result of the bug collecting process. When bug specimens are collected in large numbers from a single plant species, the presumption is that the bug breeds on that plant if nymphs are present, breeding would seem to be unquestioned. Thus, valuable information on bug behavior/biology can be acquired for the Miridae much more easily than is the case with many groups of phytophagous holometabolous insects, where rearing is required to associate the dissimilar life stages, such as moths and caterpillars.
Fig. 7. Data from Schuh (1995 and web update). Fig. 8. Data from Schuh (1995 and web update).
Like many host specific groups, species of Orthotylinae and Phylinae often have more re-stricted distributions than their hosts this in addition to the fact that a single host species may harbor several species of bugs. These patterns emerge forcefully from data in Figs. 5, 7, and 8. Thus, the amount of information on areas of endemism is greater for bugs than for hosts. For example, Schuh (2000b) showed that in western North America the widely distributed chenopodiaceous hosts Atriplex canescens which harbored 5 species of Megalopsallus Knight and the almost equally widely distributed Sarcobatus vermiculatus which harbored 7 species. Only 2 bug species had distributions anywhere nearly as broad as their host(s).
Myrmecomorphy: Ant-mimicry (myrmecomorphy), occurs widely in the terrestrial Heteroptera, including Miridae (see Fig. 1), and many other groups of insects. Both the nymphs and adults of ant-mimetic Heteroptera are usually of antlike appearance, although the different sexes and life stages may have the appearance of different ant species. At least 4 myrmecomorphic lineages have been documented within the subfamily Phylinae (Schuh, 1986 Fig. 3) the number of independent origins of myrmecomorphy in the Orthotylinae is still an open question, and could range from 2 or 3 to many. Only the type of study described in these pages will resolve this issue. McIver (1987) investigated the dynamics of the relationship between ants and mirids and found that plant bugs provided an excellent experimental system (see also Wheeler, 2001). The phylogenetic knowledge gained from this project will make possible further tests of theories, both historical and ongoing, about the forces that influence the development and maintenance of myrmecomorphy, and whether the primary operators (selective agents) are ants or other organisms. Thus, the results of this study will directly contribute to mimicry theory.
Platnick (1991) emphasized the diversity of the faunas in the southern continents, particularly the far south, pointing to the need for further study of these areas to counteract what he called the boreal megafaunal bias in the analysis of animal and plant distributions. We concur with his assessment, and believe that it applies to the Heteroptera (including Miridae) as well as to the spiders documented in detail by Platnick and co-authors (e.g., Forster et al., 1987 Platnick and Forster, 1989 Platnick, 2000, 2002). In support of this contention we refer to the work of Schuh and Slater (1995) which summarized distributions for all families and subfamilies of Heteroptera for the World. Especially in phylogenetically basal clades, we see lineages restricted to the southern continents, suggesting that detailed knowledge of the Gondwana fauna will be essential in the Heteroptera, as in many other groups, if conservation strategies are to preserve lineages as opposed to simply conserving species in terms of raw numbers.
In the classification of Carvalho (1952, 1957-1960) all tribal-level groupings within the Phylinae and Orthotylinae were cosmopolitan (Figs. 2, 3). Schuh (1974, 1976) strengthened arguments for tribal monophyly and produced several restricted distributions (Fig. 3). Schuh (1991) used phylogenetic knowledge of the phyline tribe Pilophorini to show that the most basal lineages in the clade are widespread in the Southern Hemisphere tropics, that lineages arising subsequently are restricted to the Indo-Pacific, and that only the most distal lineages occur in the Holarctic a similar pattern is seen in the Hallodapini and possibly Leucophoropterini.
Schuh and Stonedahl (1986) and Schuh (1991) used Phylinae and Eccritotarsini to analyze distributions in the Indo-Pacific. Their results corroborate in a rigorous cladistic context general propositions of distribution in the Indo-Pacific as promulgated by Gressitt (1956, 1963), van Balgooy (1971), and others, but which contradict the broad applicability of Wallace's line, a theory with little or no support from cladistic studies in many groups of insects and flowering plants.
In sum, it appears that the Orthotylinae and Phylinae offer substantial potential for in-depth biogeographic analysis and the capability for serving as strong indicators of general patterns of distribution in all continental areas and at a variety of levels in the taxonomic hierarchy, and consequently for different periods of earth history. Only large-scale taxonomic studies of the type described here will lead to persuasive global biogeographic conclusions.
Biodiversity Concepts: Surrogacy and Hotspots
Planetary biodiversity and environmental resources are in substantial decline, particularly as a result of habitat loss and degradation, over-exploitation of species, and the detrimental effects of alien species (Wilson, 1992). Of late, the status of biodiversity is being estimated on a global basis (Myers 1988, Mittermeier et al. 1999, Myers et al. 2000) through the identification of bio-diversity hotspots, which are estimated by an overlay of either centers of high species richness or high endemism and threat information (e.g., human impacts, climate change). Hotspots are being proposed as a credible method for prioritizing conservation efforts. Moreover, their use allows for a broader selection of taxa in identifying areas with high concentrations of biodiversity and makes best use of phylogenetic and collection-based information. The global perspective of the PBI program provides an ideal fit with information requirements of the "hotspot approach".
The "biodiversity crisis" argues for an urgent need to develop biodiversity indicators on a global basis. Because it is operationally impossible to have a single calculus for biodiversity, it is necessary to establish credible "surrogates", whereby one set of organisms is informative of others, particularly in relation to human impacts. The "hotspots approach", as outlined by Myers et al. (2000), predicts that higher plants and vertebrates will serve as surrogates for inverte-brates. However, recent literature (Oliver et al. 1998 Ferrier et al. 1999) indicates that although surrogacy is conceptually attractive, the identification of effective surrogates is elusive. These works suggest that plants and vertebrates are not always effective surrogates for terrestrial invertebrates because their areas of endemism are frequently not coterminous, a phenomenon we have alluded to above under our discussion of Hosts and Biogeographic Patterns.
A more promising approach to identifying biodiversity surrogates is to examine taxa with direct trophic relationships, such as phytophagous insects and their hosts. We argue in this proposal that diversity in the Orthotylinae and Phylinae is strongly correlated with plant diversity, because of the high host specificity in these bugs (Figs. 5, 7, 8). This argument is further sup-ported by work of the Australian Museum Centre for Biodiversity and Conservation Research (Major et al. in press) on Miridae associated with native cypress pine (Callitris glaucophylla).
Conservation International has produced a listing of 25 biodiversity hotspots (Mittermeier et al. 1999). Many of these are found in ecoregions of the southern continents that we argue are grossly under-sampled and inadequately documented for the Orthotylinae and Phylinae. The sampling regime we propose will target already identified hotspots such as the fynbos of South Africa, southwest Australia, and New Caledonia, among others. This study will produce, with PBI funding, documentation to refine the identification of biodiversity hotspots on a global basis.
Scientifically speaking, an insect is any member of the taxonomic class Insecta, under the subphylum Hexapoda. As you can guess from the name Hexapoda, all insects have 6 legs, which is one of their most distinguishing characteristics.
Aside from insects having six legs, there are other ways to tell whether a certain little creature is an insect or not.
An insect’s body is divided into three parts: the head, the thorax, and the abdomen. All insects have compound eyes, consisting of thousands of ommatidia, which are clusters of photoreceptor cells, making the close-up view of an insect’s eyes look like a soccer ball (just with way more hexagons and pentagons).
All insects also have one pair of antennae, as well as an exoskeleton made of chitin (which is the same as those on crustaceans, such as shrimp). This chitinous exoskeleton is pretty inflexible, meaning it can’t grow as the insect grows. This means insects must molt, which is when it sheds some of its external body parts giving it room to increase in size, and then a larger exoskeleton forms soon after.
However, in English, the word insect has multiple meanings, even if you don’t consider the colloquial usage to be just about any little living thing. Many scientists consider insects to be slightly narrower in scope (called Ectognatha), consisting of only Pterygota (winged insects), Zygentoma (silverfish), and Archaeognatha (jumping bristletails). With this definition, the other three groups are all Entognatha, which include Collembola (springtails), Protura (coneheads), and Diplura (two-pronged bristletails). One thing that this narrower definition of insects include is an external mouthpiece.
Did You Know? There are more than a million known species of insects already, making up more than 50% of all living organisms. And, scientists believe that there are many more to be discovered, and that insects could account for more than 90% (. ) of all animal life forms on Earth!
Like insects, bugs are often used colloquially in English to refer to all creepy-crawlies, as well as sicknesses, computer viruses, annoying behavior, and other problems.
However, there are “true bugs,” and they exist in the scientific taxonomic order Hemiptera.
Let me digress for a moment, if you will. In biology, there are different ways to classify and group species (called taxonomy). Though there are several different taxonomic classification systems, most look something like this, from highest level on down: Life > Realm > Kingdom > Phylum > Class > Order > Family > Genus > Species. There are other groupings, as well as sub-groupings (e.g., suborder), but this is generally how it goes.
Okay, let’s get back on track. So, Hemiptera (true bugs) is a scientific order. However, Insecta (insects) is a scientific class. As you can see, they are at different levels, and actually, Hemiptera is an order under class Insecta.
This means that all bugs are insects, but not all insects are bugs.
This also means that all bugs have the same defining characteristics as all insects, including the three-part body, the pair of antennae, the chitinous exoskeleton, and the 6 legs. However, since they’re a narrower grouping, they have some specific traits that make them different from other insects.
Bugs have a stylet, which is an external mouthpiece shaped like a straw made for what straws do best, sucking. Some bugs use their stylet to reach in there and suck nectar or sap from plants, while others suck blood from larger animals. The thin, needle-like shape allows bugs to pierce the skin to get to what they want pretty effectively.
Bugs also have wings, sometimes two sets, forewings and hindwings. The forewings on bugs are usually membranous in nature and appearing translucent, while some bugs have wings that are hardened and darker as it gets closer to where it connects to the body. Actually, the name Hemiptera means “half wing,” and they got its name from those bugs with the partially-hardened wing, as it looks like half the wing is solid, while the other half, nearer the tips, is transparent.
Bugs include cicadas, moss bugs, aphids, shield bugs, water bugs, scale insects, whiteflies, assassin bugs, and sweet potato bugs. A lot of the “hoppers,” such as treehoppers, froghoppers, planthoppers, and leafhoppers, are all bugs, as well interestingly, however, the grasshopper is not a bug, as it belongs to the taxonomic order Orthoptera rather than Hemiptera.
Did You Know? There are many little critters with everyday names such as the ladybug, the May bug, and the lovebug (not the 70’s hippie kind) that aren’t actually bugs. These belong to other taxonomic orders under Insecta. The ladybug is actually a beetle, while the lovebug is a type of fly.
Review the images for tips on how to identify these predators.
Anchor bugs look very similar to harlequin bugs, a pest insect (See comparison). Like all predatory stink bugs, Anchor bugs have beaks that are at least twice as thick as their antennae. Adults have a distinctive marking on the top of their abdomens that resembles a ships anchor. The two spots on the top of the thorax are widely separated by a large black marking, unlike Perillus. Coloration is either yellow, orange or red, with black markings. They have rounded shoulders rather than the spines seen in Podisus, for example.
No wings. Beaks like adults. The overall shape is rounded with a somewhat flattened underside. Distinctive purple-black body and orange legs.
A perfect cycle
The butterfly synchronizes its lifecycle with milkweeds by laying its eggs on the plant in the US. In fall, when the milkweeds start to die, a young generation of monarch butterflies leave for Mexico. As soon as the first milkweeds appear in spring, the monarch butterfly returns to begin the cycle anew. There's evidence that they possess a genetically coded instinct for which direction to fly.
Monarch butterflies losing ground
Tree diversity drives abundance and spatiotemporal β-diversity of true bugs (Heteroptera)
1. Spatiotemporal patterns of canopy true bug diversity in forests of different tree species diversity have not yet been disentangled, although plant diversity has been shown to strongly impact the diversity and distribution of many insect communities.
2. Here we compare species richness of canopy true bugs across a tree diversity gradient ranging from simple beech to mixed forest stands. We analyse changes in community composition by additive partitioning of species diversity, for communities on various tree species, as well as for communities dwelling on beech alone.
3. Total species richness (γ-diversity) and α-diversity, and abundance of true bugs increased across the tree diversity gradient, while diversity changes were mediated by increased true bug abundance in the highly diverse forest stands. The same pattern was found for γ-diversity in most functional guilds (e.g. forest specialists, herbivores, predators). Temporal and even more, spatial turnover (β-diversity) among trees was closely related to tree diversity and accounted for ∼90% of total γ-diversity.
4. Results for beech alone were similar, but species turnover could not be related to the tree diversity gradient, and monthly turnover was higher compared to turnover among trees.
5. Our findings support the hypothesis that with increasing tree diversity and thereby increasing habitat heterogeneity, enhanced resource availability supports a greater number of individuals and species of true bugs. Tree species identity and the dissimilarity of true bug communities from tree to tree determine community patterns.
6. In conclusion, understanding diversity and distribution of insect communities in deciduous forests needs a perspective on patterns of spatiotemporal turnover. Heterogeneity among sites, tree species, as well as tree individuals contributed greatly to overall bug diversity.
Additional Supporting Information may be found in the online version of this article:
Appendix S1. Tree diversity and sampling success.
Appendix S2. List of true bug species.
Appendix S3. Spearman rank correlations of untransformed data.
Appendix S4. Proportional data additive partitioning of true bug diversity.
Appendix S5. Proportional data species richness of functional groups/guilds of true bugs.
Appendix S6. Proportional data species richness of host plant/prey specialisation of true bugs.
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Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.
Adult annual cicadas have black, green, or olive-patterned bodies, often with a whitish cast on the underside, black or brown eyes, and 4 membranous wings with a black or green tinge. They crawl and fly but do not jump. The mouthparts, tucked beneath the head, are like a small, sharp straw. The antennae are short, and there are 3 ocelli (eyespots) in addition to the 2 larger, compound eyes. Compared to periodical (13- or 17-year) cicadas, annual cicadas are larger. Adult males have a sound-producing organ that emits a loud, raspy call used to attract females. Different species, such as the scissor grinder and buzz saw cicadas, have distinctively different types of calls and call at different times of day. Adult females have a curved ovipositor at the lower end of the abdomen, used to insert eggs into slits in twigs.
Nymphs are tan or brown, wingless, stout, with the front pair of legs specialized for burrowing in soil and for clinging onto trees as they undergo their final molt into adults.
A number of annual cicada species occur in Missouri. They can often be identified by their song, and the time of day they sing. Some notable species include
Kissing Bugs Are True Bugs
In the last couple of months, we have had some phone calls and inquiries about the kissing bug and the Chagas Disease. To learn more about the Chagas Disease visit the Center For Disease Control and Prevention and the World Health Organization.
Dr. Matt Bertone explains in a blog post that cases of the disease in the United States are rare, and most have been diagnosed by people who traveled here from outside the country.
Instead of using pesticides to control the insect, it is recommended the following strategies for keeping kissing bugs from entering homes:
- Reduce the amount of debris and vegetation directly around the home wood and leaf piles, stacked rocks and other habitats that attract rodents can also harbor the bugs.
- Repair cracks and gaps in homes use weather stripping on points of entry such as windows and doors, and make sure window screens are intact and holes are repaired.
- If you suspect kissing bugs are in your home, inspect racks and tight spaces, especially in bedrooms.
- Because lights will sometimes attract kissing bugs, minimizing the number of lights on at night will help to “cloak” homes.
But as Bertone points out, “Although these preventive measures will help reduce the chances of coming into contact with kissing bugs, in reality, it is very unlikely you would ever come into contact with one of these insects anyway.”
In his blog post, Bertone explains there are two species of kissing bugs that are native to the state and feed on the blood of vertebrate hosts. Their name comes from the fact that when the bugs feed on humans at night, they prefer the face, especially the lips and eyes. Their bites don’t initially hurt but often become itchy, swollen, and sometimes painful.
Kissing bugs are around one inch long when fully grown and somewhat flattened when not fed. They don’t have mandibles or chewing mouthparts, but instead, they have a long, straw-like rostrum used to suck liquids.
The sides of their abdomen and thorax are striped, alternating black and orange/red (sometimes even pink in hue), Berton writes, “The legs of kissing bugs are thin compared to most assassin bugs, likely because they do not need to grab prey but instead must be able to move quickly.”
Briefing Sheet: Conserving Insects on Farmland
Insects are important to the ecosystem, pollinating plants and dispersing seeds, which are vital for agriculture and food production and, in turn, have an economic impact. They control populations of other insects while also providing a food source for reptiles, birds and fish.
As discussed in the What the Science Says piece on insect declines, many insect populations are in decline, and this is a serious concern. There needs to be long-term, in-depth monitoring to understand how insect populations are faring and what is causing the declines. However, we do know ways to help with this decline, even if we do not know all the information about a specific species.
Why are they declining?
There are many reasons for changes to insect populations. These include:
- Loss and change in habitat, along with the plant species within those habitats – insect diversity is strongly linked to the diversity and number of plants.
- Climate change: insects respond quicker to changes in temperature compared to other groups of species.
- Pesticides: insecticides directly kill insects, whereas herbicides kill the weed plants on which some insect species depend on, affecting them indirectly.
How can we help?
Methods to support insect populations generally focus on the size and quality of habitat. This includes improving habitats by increasing the number of plant species and reducing dominance by any particular species. Other ways to improve quality are to create, conserve and reconnect habitats that have spilt. There are many management techniques which can benefit insects in different areas, including:
- Creating new wildflower areas
- Field margins without crops
- Unharvested cereal headlands (Conservation headlands)
- Allowing hedgerows to flower and increasing hedge bank plant diversity
- Beetle banks
- Increasing plant diversity in grassland
- Establishing new broadleaved woodland (that are still managed) and ensuring existing woodland has a plant-rich understorey
- Preserving diverse buffer strips around watercourses
- Creating nesting areas of bare ground that can support some pollinators such as solitary bee species
Supporting insect populations is not just limited to farmland and large areas. In gardens, there are two simple measures: increase the number of native plant species and keep some areas untidy. Scruffy areas with some weeds are generally good for insects. Awareness and understanding of the methods required to support and improve insect populations are vital to their success, both in the farming community and the general public. Generating public interest and creating a plan for recovery are also important for insect numbers and diversity.
Farming and agri-environment schemes (AES)
The importance of insects on farmlandPollinators are vital for crop yields.
Within an arable field, there can be between 1,500 to 3,000 different species of insects and spiders. Other habitats found in farmed landscapes also support diverse invertebrate communities, especially hedgerows, and although we don’t have an accurate estimate of the number of species, it is likely to be in the thousands, which include pests, beneficials, or those that are benign. Beneficial insects can be further classed as:
- Pest predators that eat pests either as an adult or larvae
- Pest parasites that live within the pest
- Pollinators, vital for crop yield
- Those which help break down organic matter
In an arable field up to 400 farmland predatory insect species, including beetles, spiders, mites, true bugs, flies and harvestmen may occur while surrounding non-crop habitats support many more. Consequently, there is a more diverse mix of insects and spiders within 60m of the field edge, but this decreases sharply as you move further into the field. Insects also provide a food source for farmland wildlife, such as birds, bats and reptiles.
The GWCT has conducted research on techniques to encourage beneficial insects, the natural enemies of pests, on farmland for many decades, some of this at the Allerton Project. More recently, research has been conducted with Kellogg’s Origins, investigating what is happening at the edge of crop fields and what natural resource methods would boost the number of beneficial insects, helping to control crop pests. Dr John Holland and Phil Jarvis have recently presented a seminar on ways to encourage beneficial insects and on the teams’ findings from the Kelloggs’s Origins project:
Habitat diversityFollowing SAFE (shelter, alternative prey, flower-rich, environment) principles improves the quality of the farmed landscape.
An ideal landscape would have a mix of different crops, as well as non-cropped areas, creating a diverse habitat to support the wide range of beneficial insects, as shown in figure 1 and 2. There are four key criteria that need to be met to encourage beneficial insects:
- Shelter (hedgerows, margins, areas protected from insecticides and intensive tillage)
- Alternative prey (for when there are no pests, prey can be found on other crops, uncropped areas and weeds)
- Flower-rich habitat (varied habitat and pollen and nectar plants to provide food)
- Environment (limiting insecticide use, habitat management across the farm, habitat structure and diversity and creating microclimates)
For more information on the specific sowing conditions and plants needed for the following habitats, please read the AHDB Encyclopaedia of pests and natural enemies in field crops.
Hedgerows support a great diversity of beneficial insects throughout the year, but this depends on plant composition as the number of insect species associated with trees and shrubs varies greatly. For example, hawthorn supports 209 different insect species, whereas holly only supports 10. Hedges create micro-climates with a wide range of structures, providing shelter and sources of pollen and nectar. This is especially important for insects during the winter and no crop periods as hedge flowers can provide the food to improve fitness and increase their chance of survival.
To maintain insect diversity, the hedge should contain different structures and a variety of plant species, with new planting to replace gaps, containing species that support insects. Insect numbers fall after hedge cutting therefore, hedges should not be cut yearly and not to a standard height as this doesn’t encourage new shoots. Trimming on a two to three-year rotation or by cutting incrementally at the end of the winter will help insects, hedges and flower production. Having a wide flower-rich margin between the hedgerow and arable field will act as a buffer zone, protecting the hedgerow from pesticide and fertiliser drift.
Grass margins and buffer zones are important, supporting a wide range of insects, especially through the winter by providing alternative foraging areas. Tussocky grasses are a particular favourite of beetles and spiders. Grassland is also likely to be beneficial if it is lightly managed and has a diverse mix of grass and herbaceous species. A range of grasses can create a variety of microclimates which will help support insects that are less able to control their body temperature, and are host plants for many butterfly and moth butterflies. Non-aggressive fine-leaved grasses are recommended, common bentgrass, crested dog’s-tail and sheep fescue.
Flower-rich habitats can provide multiple resources for beneficial insects such as foraging, breeding, and overwintering sites. In agri-environment schemes, the first and simplest option to be developed was the pollen and nectar mixes, now known as nectar flower mixes. They typically include clovers, vetches, bird’s-foot trefoil and sainfoin, which are preferred by long-tongued bumblebees and some butterflies. Flower-rich areas can also be created using a mix of fine grasses and perennial flowering plants, for example, knapweed, scabious, yarrow and bird’s-foot-trefoil.
The composition of these mixes is important and should be suitable for local conditions, especially soil type. To encourage a wider range of insects they can be diversified with flowers that have simple, open structures that allow for easy access to the nectar and pollen. For example, wild carrot, hogweed, cow parsley, angelica and yarrow are good options. Flowers with more complex structure encourage a more diverse range of bees, parasitic wasps, hoverflies, and flies with piercing mouthparts such as house flies, crane flies and bluebottles. Annuals are also useful for supporting beneficial insects, especially parasitic wasps and can be rotated with crops, for example, phacelia, buckwheat, alyssum, dill and coriander.
Parasitic insects are important for pest control on food plants but most need to move between crop and non-crop areas. They also need access to a source of nectar for nutrients, hence extra flowers would increase the levels of parasitic insects. Some species feed on weeds and their seeds while others consume fungi, which can reduce the need for weed and disease control.
Beetles and spiders like to overwinter in grasses because they provide stable environmental conditions even during the cold. They are good for pest control but this can only be achieved on large fields if beetles and spiders are spread across the field in the spring. In fields larger than 16ha, it is recommended to divide them with beetle banks. Beetle banks are raised strips, sown with a fine and tussocky grass mix, creating drier conditions favoured by insects. Wider strips can house more predators and are a better buffer from sprays.
Ideally, there should be no more than 150m between banks, encouraging both insects and other wildlife, such as birds. Beetle banks and other non-crop habitats reduce the distance over which these beneficial insects must migrate into fields. This will ensure a more even coverage, helping to control crop pests and potentially reducing the need for insecticides as well as increasing connectivity between these habitats.Figure 1: The managed habitat created by crops and weeds influenced by the type and abundance of beneficial insects, from “Beneficials on farmland: identification and management guidelines”. Figure 2: Best practice to encourage beneficial insects in the field, from “Beneficials on farmland: identification and management guidelines”.
Many insects have life-stages in the soil, with large numbers of beneficial insects overwintering in the fields, including beetles, flies and spiders. These soil-based insects have important roles in recycling nutrients and controlling crop pests but turning the soil over with ploughing can disturb and kill them. Therefore, using non-inversion tillage practices will allow for beneficial insects to survive. The timing of seedbed preparation can also impact insect survival, along with the type of crop and associated pesticide use. Other measures such as under sowing cereal crops to establish a grass ley also helps soil living insects as the ground remains undisturbed.
Farming a varied mix of crops will help support a diversity of insects, lowering the risk of pest outbreaks. One of the biggest issues is crop type and the associated insecticides and herbicides used. Spring root crops come with more intensive soil cultivation, leading to fewer beneficial insects. How quickly insect numbers recover after this level of disruption depends on the surrounding area. In block cropping (the same crop in adjacent fields), recovery is slow and pest populations increase because there are fewer predators and parasites. Diversity in crops and having untreated fields nearby will help with recovery, lowering the pest risk.
Insecticides and herbicides
Although some insects (pests) do feed on crops, very few cause economic damage because they are a food source for other insects. If the conditions change, favouring the pest or causing predator numbers to reduce, a pest outbreak develops. Farmers need to control agricultural pests, but insecticide kills a much broader range of insects including the beneficial ones. Furthermore, if the insecticide doesn’t remove all the pests but does remove the predators, this may lead to a pest outbreak. To reduce the impact of insecticides, they must be applied when only necessary, examining pest numbers and economic damage, then only applying to areas where there is damage, instead of to every field.
The most widely used insecticides, the pyrethroids, have a broad spectrum, leading to widespread impacts on beneficial insects. There is also a range of selective insecticides such as the carbamate insecticide Pirimicarb that targets aphids on a variety of crops, although even this product had some impact on non-target insects. Adopting Integrated Pest Management – the encouragement of natural pest enemies such as beneficial insects – can help allow farmers to reduce pesticide inputs but maintain yields.
Herbicides are also an issue, as they remove host plants. Weeds are very useful, providing an alternative food source by producing nectar, pollen and seeds and supporting herbivorous insects that act as alternative prey for pest natural enemies. They also create a diverse habitat and microclimates, supporting a wide range of insects, which, in turn, support farmland birds.
Arable plants (sometimes weed species) are also often visited by a range of wild bees and typically have simple flower structures that attract a broad range of insects. Allowing some of the less competitive weeds to survive by using selective herbicides, lower dosages and patch spraying more noxious weeds, can create a more beneficial environment. A range of insects, including beneficial insects, are also found in a range of AES options (see below) including unharvested cereal headlands (conservation headlands), wild bird seed mixes and with the option “cultivated areas for arable plants” that was specifically designed to encourage the rarer arable plants. This also attracts a broad suite of insects including many pest natural enemies. Weeds can also be left by not having pre or post-harvest herbicide treatments, this will provide more food resources for predatory insects. Keeping the field uncultivated throughout the autumn will lead to more seeds on the surface for insects and birds. Overall, minimising herbicide use and leaving areas scruffy is generally a good thing for insects.
Agri-environment scheme (AES)
The cost of enhancing habitats on UK farmland for insects can be recovered through some options in the national agri-environment scheme (AES). There are different levels available including entry, organic entry and higher level, along with the Rural Stewardship Scheme in Scotland and Tir Cynnal and Tir Gofal in Wales. Levels of pollination can be lower in larger fields because insects have to travel further into the crop, but larger fields are more economical to farm, so AES or other financial support may be needed to tip the balance in favour of smaller, more ecologically beneficial fields.
Agri-environment schemes need farmers that are willing to cooperate with each other. A study interviewing British farmers found there was a lack of communication between them. The authors suggested an external organisation to oversee joint operations and break down barriers, which 80% of the farmers interviewed approved of. The authors also suggest creating more collaborative agri-environment schemes, a more attractive option for farmers and likely to increase overall uptake to the schemes. This would involve farmers working with other farmers on an agri-environment scheme, instead of on their own, for example creating a network of hedges. Furthermore, they found farmers were more willing if they could enter part of their farm into the scheme so the ecological outcomes are achieved but the farmer can be more flexible. Since those proposals in 2012, farmers have started working together as Farmer Clusters and the approach has gained momentum, with over 150 clusters formed by 2020 across the UK. This is a farmer-led initiative in which they make the decisions about how to improve their clusters to achieve environmental gains. For more information about the approach, visit www.farmerclusters.com.
Public awareness of insects and their decline
Awareness of and interest in insect conservation is lower than for mammals and birds, and therefore there is a lack of public engagement. Most insect species are not an attractive cause that appeals to the public, especially when the media is full of images of other animals that are more impressive, cute and cuddly, such as tigers, pandas and elephants, which have benefited from marketing. All species are important, as is their conservation, but the awareness and coverage of some are limited because there is either no monetary gain or they just don’t come across as exciting. For example, bumblebees have a cute appeal which recently attracted more attention. Honeybees are vital for pollination, linked to food production, and butterflies are beautiful and eye-catching, therefore they are in the public eye. If people start to understand insects and care enough for them, and see them as a valuable commodity, there will be more drive to preserve them.
The key is to increase understanding of the different types of insects, their diversity and what they can offer. The use of “decline” when describing insect numbers might not be as effective to gain public support and action instead, gaining knowledge about what is happening to them and communicating this, along with what it means to people, may be more successful.
The bigger picture: Roadmap to recovery
Figure 3: The road map to recovery for insects, eight no-regret solutions taken from Harvey et al, 2020.
A roadmap to insect conservation and recovery was published in early 2020, arguing that although our knowledge about insect populations is far from complete, we know enough to act now on their conservation, and laying out eight no-regret solutions that could be adopted immediately to address this problem. These are proposed to be beneficial to society and biodiversity, even though their direct impacts on insects may not yet be fully known. The authors urge that, despite the knowledge gaps, action should not be delayed while we address them. They propose that enough is known to act now, whilst continuing with research in the areas that are still unclear and monitoring the impact of their proposals. These are illustrated in the diagram below:
Insect populations are often undervalued, but they provide the foundation for ecosystems and food webs the world over. As described in a report by the Zoological Society of London for the IUCN in 2012, “if invertebrates were to disappear tomorrow, humans would soon follow”
They also proposed multiple research aims to focus on to help understand the changes in insect numbers and diversity, including quantifying the trends in insect numbers over time to provide a new census long-term studies comparing insect numbers and diversity between different habitats to understand what could cause differences applying a standard monitoring system globally along with long-term monitoring sites that those are applied to and protecting, restoring and creating new insect habitats. They conclude that “a ‘learning-by-doing’ approach ensures that these conservation strategies are robust to newly emerging pressures and threats”.
In arable farmland, to maintain pest control but also support these beneficial insects, these practices are recommended:
- Maintaining or creating flower-rich field margins, providing nectar and pollen for a wide variety of species.
- Create beetle banks in fields greater than 16ha so wintering insects can control pests on cereal crops in the spring.
- Plant new hedgerows in fields that contain beneficial plants.
- Use selective insecticides such as pirimicarb when needed and only on the area infested, using pest spray thresholds, and avoid prophylactic insecticide.
- Avoid complete weed control as weeds provide food and habitat for insects important for pest control.
- Create conservation headlands around the edges of cereal crops.
- Use non-inversion soil tillage.
- Have a diverse crop rotation and avoid block cropping.
At home, in gardens, simple measures can be taken:
- Increase the number of native plant species.
- Leave some areas untidy weeds and scruffy areas are generally good for insects.
Public awareness needs to increase, helping the public understand all the benefits that insects offer and why it is so important to increase their numbers and diversity.
14 Darling Facts About Ladybugs
Ladybugs are familiar and beloved fixtures of our gardens, but there’s more to them than cuteness. Take a second look at these backyard insects.
1. LADYBUGS ARE NAMED AFTER THE VIRGIN MARY.
There are both male and female ladybugs, so why do we call them “ladies”? According to Oxford Dictionaries, they’re named after one particular lady: the Virgin Mary. One of the most common European ladybugs is the seven-spot ladybug, and its seven marks reminded people of the Virgin Mary’s seven sorrows. Germans even call these insects Marienkäfers, or Mary’s beetles.
2. THEY AREN’T BUGS.
Ladybugs aren’t bugs—they’re beetles. True bugs belong to the order Hemiptera, and these include familiar insects such as bedbugs and cicadas. Ladybugs, on the other hand, are part of Coleoptera, the beetle order. Many entomologists prefer to call them “lady beetles," or Coccinellids.
3. SOME PEOPLE CALL THEM BIRDS, BISHOPS, OR … COWS.
In parts of England, and for reasons that are unclear, the ladybug is a bishop. Local variants of this name abound, including the amazing bishy bishy barnabee. Nowadays, most people in England use the word ladybird, perhaps because these insects are able fliers.
In several languages, the portly, spotted ladybug is affectionately known as a little cow. For example, a popular Russian name for the ladybug is bozhya korovka, which translates to “God’s little cow.” French people sometimes use the term vache à Dieu, which means “cow of God.” And the English once called it a ladycow before they switched to bishop and ladybird.
4. THEY COME IN A RAINBOW OF COLORS.
You’ve probably seen red ladybugs with black spots—but members of the ladybug family come in a wide range of hues, from ashy gray to dull brown to metallic blue. Their patterns vary, too some have stripes, some have squiggles, and some have no pattern at all. Among the spotted ladybugs, the number of spots varies. The twice-stabbed ladybug is black with just two bright red dots. On the other hand, the yellow twenty-two spot ladybug has, well, 22 of them.
And some ladybugs just like to make things complicated. The harlequin ladybug can be yellow, red, black, and almost any combination thereof, and it has any number of spots, from zero to 22.
5. THOSE COLORS ARE WARNING SIGNS.
If you’re an animal, one way to avoid being eaten is to be toxic—or just plain foul-tasting. Many animals produce chemicals that make them taste gross, and they warn predators about their yuckiness with blazing bright colors—sort of like a stop sign or yellow caution tape.
Striped skunks, for example, pack a powerful stinky spray, and their black and white pattern serves as a warning sign. Highly venomous coral snakes wear vibrant red, black, and yellow stripes. Similarly, ladybug species with bright colors are walking billboards that say, “Don’t eat me. I’ll make you sick.” And that’s because …
6. LADYBUGS DEFEND THEMSELVES WITH TOXIC CHEMICALS.
Okay, don’t panic. Ladybugs won’t harm you unless you eat many pounds of them (or in the rare case that you’re allergic to them). But a lot of ladybugs produce toxins that make them distasteful to birds and other would-be predators. These noxious substances are linked to a ladybug’s color the brighter the ladybug, the stronger the toxins.
7. THEY LAY EXTRA EGGS AS A SNACK FOR THEIR BABIES.
Ladybug moms lay clusters of eggs on a plant (here’s a video of egg laying in action). But not all of those eggs are destined to hatch. Some of them lack embryos. They’re a tasty gift from the mother ladybug the newly hatched babies will gobble them up.
8. BABY LADYBUGS LOOK LIKE ALLIGATORS.
When you think “baby ladybugs,” you might imagine that they look like adult ladybugs—but smaller. Cute, right? But this is what hatches out of those ladybug eggs. It’s a long, spiny larva that looks a little like an alligator.
Though ladybug larvae may be intimidating, they’re not harmful to humans. They crawl around, feeding and growing, until they’re ready to turn into something even weirder …
9. LADYBUG PUPAE LOOK LIKE ALIENS.
The next step in a ladybug’s life cycle is to find a nice spot on a piece of vegetation, settle down, and become an alien-looking pupa. Protected by a hard covering, the ladybug then makes an incredible transformation from larva to adult, breaking down old body parts and creating new ones. And once the adult is ready to emerge, it bursts out of its old skin.
10. ADULT LADYBUGS FLY WITH HIDDEN WINGS.
Ladybugs don’t look very aerodynamic. Their colorful domed backs are made of modified wings that are basically hardened armor. Flapping them would get a ladybug nowhere fast. So how do these insects fly?
When a ladybug takes off, it lifts up those protective covers. Underneath is another pair of wings that are slender and perfect for flight. Normally folded for easy storage, they unfold for takeoff.
11. LADYBUGS SURVIVE THE WINTER AS ADULTS.
We associate adult ladybugs with bright summer days—but they’re around even in the depths of winter. They enter a state of rest and cuddle together in groups, often in logs or under leaves.
One species, the harlequin ladybug, keeps toasty by entering our homes. These insects will gather in huge numbers and settle into dark crevices in a house. On unseasonably warm days, they wake up and blunder around the room. Fortunately, these insects don’t eat our food or chew on our furnishings. But they do squirt out a noxious defensive liquid that can stain light surfaces. Also, they can sometimes cause allergic reactions.
12. THEY’RE VORACIOUS PREDATORS—MOSTLY.
Ladybugs are universally beloved, and one reason is that they’re a natural (and adorable) form of pest control. They eat plant pests such as aphids, scale bugs, and mealybugs, and they have huge appetites: a single ladybug can eat 5000 aphids across its lifetime.
But many ladybugs supplement their diets with pollen and other plant foods. Some eat vegetation and fungi exclusively. The orange ladybug, for example, munches on mildew. For some, garden plants are on the menu: the Mexican bean beetle dines on beans, and the squash beetle eats squash, cantaloupe, and pumpkin.
13. WE’RE SPREADING LADYBUG SPECIES AROUND THE WORLD.
Some ladybug species have turned up in parts of the world where they weren’t previously found. They’ve spread in a couple of ways: in some cases, people brought over the insects to combat agricultural pests, and in other cases, the bugs hitchhiked on imported goods.
The results haven’t always been beneficial. One invader, the harlequin ladybug, is native to East Asia but has spread to parts of Europe and North America. It pushes out native species, infects them with a deadly fungal parasite, and even eats them.
14. THEY CAN BE BAD FOR YOUR WINE.
Thanks to harlequin ladybugs, winemakers face a new and bizarre problem: ladybug taint.
Many vineyards are situated near fields of other crops such as soybeans. Ladybugs eagerly devour the aphids that infest those crops, but once the crops are harvested, the insects need a new place to hang out. Some of them wander over to the vineyards and crawl around on the grapes.
But then comes the grape harvest. The insects are accidentally scooped up with bunches of grapes—and when ladybugs are frightened, they squirt out a smelly defensive fluid. The resulting wine has a particular stinky flavor that has been likened to peanuts or asparagus. Cheers!
How Not to Be Eaten The Insects Fight Back
Insects constitute by far the largest amount of animal food available to flesh eaters both on dry land and in freshwater. The one quarter of the earth that is not covered by the oceans and seas is inhabited by an immense and not yet completely censused population of insects. The 900,000 currently known insect species (at least three million are yet to be discovered and named, according to reasonable estimates [Stephen Marshall]) constitute about 75 percent of the currently known 1,200,000 animal species on land, in freshwater, and in the oceans. The Canadian entomologist Brian Hocking made the daring but educated guess that the world population of insects is about one quintillion (1 followed by eighteen zeroes) individuals. Even if he overestimated by trillions, that would still be a stupendous population.
Although insects are small, they are generally so numerous in most terrestrial and freshwater ecosystems that, on a per-acre basis, they not only outnumber but also outweigh all the other animals-including deer and moose-combined. On the face of it, this is hard to believe. But keep in mind that a single acre of land may be home to many millions of insects of hundreds or even thousands of species. By contrast, the home territory of one small bird is likely to encompass as much as an acre, and that of a large mammal, such as a thousand-pound moose, several hundred or even thousand acres. Thus the biomass of an animal that weighs hundreds of pounds may be much less that one pound per acre. Also keep in mind that most people notice only a few of the many insects around them, perhaps a ladybird beetle or a large and beautiful butterfly but more often the insects that sting, bite, or otherwise annoy them. Yet the other insects, by far the vast majority in almost any ecosystem, go unnoticed. Not only are they small, but many are difficult to see because they are camouflaged, and many are out of sight because they live in the roots, stems, or other parts of plants as parasites within the bodies of insects and many other animals or in the soil or other cracks and crevices of the environment.
Insects are, either directly or indirectly, the most plentiful source of flesh for animals that don't eat plants. But they are important to these predators not just because of their abundance. Plant-feeding insects, estimated to be about 450,000 species, and the insects and other animals that eat them are by far the most important link between green plants and animals that don't eat plants, a conduit through which predators receive the energy of the sun, which green plants-and only green plants-can capture and make available to animals via photosynthesis, in the form of sugars. Insect-eating insects play another significant, although less important, role. By eating tiny organisms and incorporating their prey's nutrients in their own bodies, large insects become "nutrient packages" for large insectivores that cannot profitably pursue and eat tiny organisms themselves.
Data gathered by Eugene Odum and other ecologists show just how important a part of the food chain insects are in specific ecosystems. For example, in a field of herbaceous plants in North Carolina, the biomass of the plant-feeding insects alone-not including any predaceous, parasitic, or scavenging species-was nine times greater than that of sparrows and mice, the larger and more conspicuous and by far the most numerous of the vertebrates in that field. On an East African plain, just two species of ants-only those two, among hundreds of other kinds of insects-were about equal in weight, per acre, to the combined weight of the large grazing animals, such as wildebeests, zebras, and antelopes. In these two habitats and in almost all others, insects are by far the most abundant of the prey animals in both numbers and biomass. As is to be expected, and as we will see in the next chapter, hundreds of thousands of different kinds of animals exploit this nutritious, protein-rich food: spiders, scorpions, insects, frogs, toads, lizards, birds, mammals.
The insects almost certainly have more different lifestyles, ways of surviving and "making a living," than do any other group of animals. One species or another occupies every-or nearly every-ecological niche. An ecological niche is not just a place it includes all of the resources, food, nesting sites, hiding places, and so on, required by an organism. Except for aquatic species, insects that undergo gradual metamorphosis occupy essentially the same niche throughout their lives. Those with complete metamorphosis often occupy two very different niches in their larval and adult stages.
Dragonflies, grasshoppers, cockroaches, mantises, true bugs (order Hemiptera), and lice are some insects that gradually metamorphose. A newly hatched grasshopper-a nymph-looks very much like its parents but lacks wings. As it grows, it molts several times, and its developing wings, which are external, can be seen gradually increasing in size until the hopper stops growing and molts for the last time to become an adult with flightworthy wings. Insects with gradual metamorphosis have only three life stages: the egg the nymph, the growing stage and the adult, the egg-laying reproductive stage. Nymphs look and behave much like adults, except in most aquatic species. For instance, adult dragonflies are aerial acrobats that pursue flying insects. But the nymphs are aquatic, don't look at all like the adults, and are fierce predators that eat aquatic insects and even small fish.
Beetles, fleas, flies, wasps, bees, moths, and butterflies are among the many insects that undergo a complete metamorphosis. The baby butterfly just hatched from the egg is a wormlike larva that does not at all resemble its parents. A biologist from another planet might think that the larva and the butterfly are two quite different kinds of animals, as dissimilar as birds and snakes. Complete metamorphosis proceeds in four life stages: the egg the wingless larva, called a caterpillar in the case of butterflies and moths the pupa, the transition stage in which the larva metamorphoses into the adult and the winged reproductive stage. Larvae not only look different than their parents but also usually behave very differently. Caterpillars, for example, have chewing mouthparts, and most feed on plants, usually the leaves. The wingless pupae, with only a few exceptions, can squirm but cannot walk or crawl and are usually tucked away in a safe place, perhaps in the soil, under bark, or in a silken cocoon. The adult, a butterfly or moth for example, has large wings that developed internally in the pupa, as do its long, soda straw-like siphoning mouthparts, used for sucking nectar from blossoms.
The larvae and the adults are specialists, anatomically and behaviorally equipped to do particular tasks. The larvae eat, grow, and do their best to foil predators. The adults suck the sugary nectar that supplies energy to fuel their frequent flights as they seek mates and as the females distribute their eggs. Most butterflies and moths, as well as many other insects, glue their eggs only to one of the few plant species their fussy-host plant-specific-offspring will be willing to eat. The larvae are "eating machines," and the adults are flying gonads or, as Carroll Williams said, "flying machines devoted to sex." Because of the benefits of such specialization, complete metamorphosis has been an evolutionarily more successful strategy for survival than gradual metamorphosis, at least as judged by the number of known insect species on earth today-only about 135,000 (15 percent) with gradual metamorphosis, while 765,000 (85 percent) have complete metamorphosis.
Insects with either type of metamorphosis can occupy similar ecological niches. Grasshoppers, Japanese beetles, June beetles, and many other insects occupy fairly commonplace niches. The adults feed on foliage and lay their eggs in the soil. However, after hatching from the egg, nymphal grasshoppers immediately make their way to the surface and feed on the leaves of grasses or herbaceous plants, while the white C-shaped larvae, known as grubs, of the two beetle types, which both have complete metamorphosis, remain in the soil and feed on plant roots. They pupate in the soil, and the adults dig their way up to the surface after they have shed the pupal skin.
Other insects have more complex and elaborate lifestyles. For example, a male burying beetle whose search for a dead animal has been successful sits on the body of the small dead animal he has discovered and releases a scent, a sex-attractant pheromone. A female soon joins him, and, working together, they burrow back and forth beneath the dead body until it sinks deep enough into the ground so that they can cover it with soil. Then they create an open space underground around the buried carcass and cover the dead animal with a secretion that kills bacteria, thereby delaying decomposition. The female then lays as many as thirty eggs in the soil near the carrion. After the larvae hatch, they crawl to a nest prepared by their parents, who feed them by regurgitating predigested carrion. Eventually the larvae feed on their own. The father then leaves, but the mother guards her young until they are ready to pupate. In a few weeks her offspring emerge from the soil as adults and begin another cycle.
Elsewhere, a tiny female gall wasp inserts an egg into an oak leaf. As May Berenbaum wrote in Bugs in the System, gall makers commandeer "the plant's hormonal system in such a way that the plant is induced to produce bizarre and unusual growths [galls], which provide the insect with a place to live and with nice nutritious tissue on which to feed." The larva that hatches from her egg causes the oak leaf to form an abnormal growth, in this case an "oak apple," a light tan spherical gall that may be as large as a table tennis ball. Another gall maker, a moth, lays an egg in the stem of a growing goldenrod in spring, causing the plant to produce an egg-shaped thickening almost an inch in diameter. In summer the caterpillar grows to full size. The following spring it gnaws an exit hole through which, after it pupates, it will emerge as a moth. But it may not survive that long. In winter a hungry downy woodpecker may peck a hole in the gall, pull out the caterpillar, and make a meal of it.
These few examples give no more than an inkling of the many different ways in which insects conduct their lives. Insectivores must, of course, have the anatomical and behavioral adaptations required to catch their prey. A bird, for example, can snatch an adult grasshopper, beetle, gall wasp, or gallfly from the air with its beak, but only a tunneling animal or a bird that probes in the soil is likely to find subterranean eggs, grubs, or pupae. Only a woodpecker is likely to get at a larva in a gall or burrowing under the bark of a tree.
The evolution of the millions of different kinds of insects that live on earth now and the many extinct species that we know only as ancient fossils began about four hundred million years ago, when the first insects-to-be were gradually leaving the water, where life began, to move onto the land. They probably reached the shore via moist organic debris at the edges of freshwater ponds and once on land probably continued to feed on soft rotting organic matter, which they ate with their primitive, unspecialized mouthparts, the organs of ingestion. From these simple creatures evolved the diverse assortment of modern insects, as different from one another as grasshoppers with mouthparts specialized for chewing on plants, butterflies with tubelike mouthparts for sucking nectar from flowers, and mosquitoes with piercing-sucking mouthparts for consuming the blood of birds, mammals, or reptiles.
Plants and animals, of course, continue to evolve. But how does evolution work? Charles Darwin had the brilliant insight that natural selection is the driving force of evolution, producing new species just as breeders produce new dog breeds through artificial selection, by selecting animals with desirable traits to be the parents of the next generation. (Keep in mind that all breeds, from the tiny Chihuahuas to the huge Saint Bernards, are descended from the wolf.) Natural selection, while tending to cull poorly adapted individuals, favors those better adapted to avoid hazards and to take advantage of opportunities. For example, an individual with even slightly better camouflage than others will be somewhat less likely to be noticed by a predator and, consequently, somewhat more likely to survive and become a parent. Heritable adaptive traits are passed on to future generations and given enough time will spread to all members of a population. As the centuries or millennia pass, more favorable mutations accumulate in a population until those who have them are so different from the other members of their species that they become a separate, distinct, reproductively isolated species, one whose members do not breed with members of other species.
These new adaptive traits constantly arise as genetic mutations caused by means such as radioactivity, ultraviolet light, cosmic rays, or intrinsic factors in DNA, the genetic material itself. Mutations are random, some favorable and many unfavorable. However, evolution is by no means a random process it is directed by natural selection, which tends to eliminate unfavorable mutations and generally perpetuates favorable mutations. Think of a prospector panning for gold. He scoops up a mixed assortment of sand, pebbles, and-with luck-a few bits of gold. But only the heavier flakes and nuggets of the valuable gold survive the panning. They are not, unlike the lighter, valueless mixture of sand and gravel, washed out of the pan as he swirls the water. In a similar way, natural selection preserves favorable genes and eliminates deleterious genes.
Some of the insects' most important adaptations are responses to insectivores, a numerous and pervasive threat to their survival. The ultimate goal of any organism is, of course, to reproduce itself, to pass its genes on to future generations, and to accomplish this it must survive long enough to attain sexual maturity. As the great English naturalist Henry Bates wrote in 1862 in "Contributions to an insect fauna of the Amazon Valley, Lepidoptera: Heliconidae":
Every species in nature may be looked upon as maintaining its existence by virtue of some endowment enabling it to withstand the host of adverse circumstances by which it is surrounded. The means are of endless diversity. Some are provided with special organs of offence, others have passive means of holding their own in the battle of life. Great fecundity is generally of much avail. A great number have means of concealment from their enemies, of one sort or another. Many are enabled to escape extermination or obtain subsistence, by disguises of various kinds: amongst these must be reckoned the adaptive resemblance of an otherwise defenceless species to one whose flourishing race shows that it enjoys peculiar advantages.
The last sentence refers to the fascinating subject of the last chapter of this book, harmless insects, and a few other harmless animals, that foil predators by bluffing, mimicking the appearance and even the behavior of other insects or other animals that sting, are unpalatable, or are avoided by predators for other reasons.
Besides reproducing themselves, insects perform indispensable ecological services. As discussed above, they are the most important link between plants and animals that don't eat plants, and they have other important roles in virtually all terrestrial and freshwater ecosystems. One of their major functions, which we have all heard about, is to pollinate plants. Most of the green plants are flowering plants, called angiosperms (Greek for "a seed encased by an ovary"), and except for hummingbirds, bats, and just a few other animals, it is the insects that transport the sperm-containing pollen from the male parts of one flower to the female parts of another. Most flowers have coevolved with bees, butterflies, or other pollinators. Their colors and scents attract insects and reward them with nectar and pollen, which many insects eat and which are virtually the only foods consumed by the thousands of species of bees (at least 3,500 in North America alone). No one knows how many of the flowering plant species are pollinated by insects, but Stephen Buchmann and Gary Nabhan have reported that of the 94 major crop plants on earth, the wind pollinates 18 percent, insects 80 percent, and birds 2 percent.
Insects have many other functions in the web of life, only a few of which I will mention here. Plant-feeding insects help to keep plant populations from increasing to a size that would disrupt a stable ecosystem. For example, when the European Klamath weed, also known as St. John's wort or locoweed, reached California, its population exploded because it had no natural enemies there it choked out grasses in pastures to the extent that they were useless for grazing cattle. After a European leaf beetle that eats Klamath weed was introduced into California, the weed became scarce, and grew mainly in shady places, where it was less likely to be attacked by the leaf beetle. An agricultural entomologist remarked that insects are their own worst enemies. And indeed they are. Thousands of insects, probably more than 300,000 of the known species, eat other insects. As Peter Price noted, insects, mostly ants, are the "world's premier soil turners," more so than earthworms, which are generally given credit for this. Without the scarabs and other dung-feeding insects, we might, to use a bit of hyperbole, be knee-deep in excrement. Furthermore, ants and other insects disperse the seeds of some plants.
In the next chapter we will meet a few of the many animals-spiders, scorpions, toads, birds, bats, mice, and even bears-that eat insects. The threat to the insects from these insectivores is enormous, but as we will see in following chapters, insects have evolved many, often amazing ways to avoid being eaten. But keep in mind that neither insects nor other organisms are completely immune to predation. If they were, their populations would probably explode, causing ecological havoc.