Information

Is this species a variant of a red flour beetle?


Found this little guy crawling around the back garden - South Coast of the UK.

The closest things I could find online (with an admittedly weak knowledge of where to look up these things, aside a google search forred beetle) were the red flour beetles. However, it doesn't look quite like what we had, this being more stockier, with a dark head, and more splayed feelers.


This does not look like a red flour beetle, but more like some species of Melolontha, possibly a cockchafer. For more specific information, we would need to know, where your back garden is and maybe something to scale the bug. I would go for Melolontha melolontha, the common cockchafer. Of the two other european species of Melolontha, M. hippocastani usually has a black edge of the elytra (see this picture), which this one doesn't seem to have, and M. pectoralis is very rare and mostly (only?) found in Germany.


I totally agree with skymningen, definitely a cockchafer


Stored Product Pests

Linda J. Mason, Extension Entomologist

If you want to view as pdf, click here

DESCRIPTION

These two beetles are often grouped together due to the similarity in their appearance, biology, and behavior. The confused flour beetle was named because of the confusion over its identity. The red flour beetle is named after its rust-red color. The two can be easily separated based on antennal characteristics. The antennae of the red flour beetle is distinctly club-like, with a three-segmented club. The club of the confused flour beetle antennae is four segmented and forms the club gradually. Another slight difference is in the shape of the thorax. The sides of the red flour beetle are curved, whereas the thorax of the confused flour beetle is straight. Both species are cosmopolitan in their distribution. Adult beetles are approximately 3.5 mm (1/7”).

Larvae of both species are nearly indistinguishable. They are a light honey color and about 6 mm (1/4”) long. The head and a distinctive forked process at the tip of the abdomen are slightly darkened.

Red flour beetle on left and confused flour beetle on right. (Photo Credit: John Obermeyer)

BIOLOGY AND BEHAVIOR

Eggs are deposited directly in flour, other food material, or attached to the surface of the container. They are white or colorless and covered by a sticky material to which flour can adhere. Eggs hatch in 3-5 days at 32-35˚C (89.6-95˚F). Larvae burrow into kernels of grain but may leave their burrows in search of more favorable food. There at 5-11 larval instars (7-8 is usual), the variation a result of environment, food, temperature, humidity, or the individual insect. Larvae are fairly active but generally hide within the food, away from light. Pupae are naked, without protection of any form. Development time from egg to adult varies with conditions, however, the average is 26 days at 32-35˚C (89.6-95˚F) and >70% Rh. The minimum, maximum, and optimum temperatures for development of the confused flour beetle are all about 2.5˚C lower than the red flour beetle. Limits of development are imposed mostly by larval mortality, esp. among early instars. The minimum temperature for development is between 20-22˚C (69-71.6˚F), the maximum 37.5-40˚C (99.5-104˚F) when the relative humidity is either low (10-30%) or high (90%). Flour beetles can survive in grain with moisture contents as low as 8%. Average fecundity is 400-500 eggs per female, with peak oviposition occurring during the first week. Adults may live longer than 3 years, and females may lay eggs for more than a year.

Red flour beetle lifecycle. (Photo Credit: John Obermeyer)

Red flour beetle adult. (Photo Credit: John Obermeyer)

Confused flour beetle adult. (Photo Credit: John Obermeyer)

Adults of both species have well developed wings, but only the red flour beetle has been observed to fly, and it is not a strong flyer. When agitated or crowded, they may secrete chemicals called quinines. These chemicals can cause the infested feed to turn pink and have a pungent odor. Confused flour beetles have been reported to prefer, and aggregate in flour exposed to quinines, whereas quinines repel red flour beetles.

Flour beetles can be found infesting a variety of grain and food materials. They have been reported from grain, flour, and other cereal products, beans, cacao, cottonseed, shelled nuts, dried fruit, dried vegetables, drugs, spices, chocolate, dried milk, animal hides, herbarium and museum specimens. They cannot feed on whole grain, but can feed on broken kernels that are usually present. In general, fungi may play a significant role in the nutrition of flour beetles.

READ AND FOLLOW ALL LABEL INSTRUCTIONS. THIS INCLUDES DIRECTIONS FOR USE, PRECAUTIONARY STATEMENTS (HAZARDS TO HUMANS, DOMESTIC ANIMALS, AND ENDANGERED SPECIES), ENVIRONMENTAL HAZARDS, RATES OF APPLICATION, NUMBER OF APPLICATIONS, REENTRY INTERVALS, HARVEST RESTRICTIONS, STORAGE AND DISPOSAL, AND ANY SPECIFIC WARNINGS AND/OR PRECAUTIONS FOR SAFE HANDLING OF THE PESTICIDE.

It is the policy of the Purdue University Cooperative Extension Service that all persons have equal opportunity and access to its educational programs, services, activities, and facilities without regard to race, religion, color, sex, age, national origin or ancestry, marital status, parental status, sexual orientation, disability or status as a veteran. Purdue University is an Affirmative Action institution. This material may be available in alternative formats.

This work is supported in part by Extension Implementation Grant 2017-70006-27140/ IND011460G4-1013877 from the USDA National Institute of Food and Agriculture.


Tribolium 101: Identifying a Flour Beetle

  • Tribolium castaneum – red flour beetle
  • Tribolium confusum – confused flour beetle
  • Tribolum destructor – destructive flour beetle
  • Tenebrio molitor – mealworm beetle
  • Tenebrio obscurus – mini mealworm

Each species possess distinctive physical (and biological) features, but all share common traits that groups them into the Tribolium genus.

Flour beetles are holometabolic meaning they undergo the complete metamorphosis life cycle from egg -> larva -> pupa -> adult .

The life span of an average adult flour beetle is approximately three years. A single adult female can lay up to 450 eggs in her lifetime at a rate of 2 to 3 eggs a day. Eggs will hatch into larvae into 5 to 12 days and become full-grown in about 30 days. The larval stage usually goes through 7 to 8 instars and grow to around 3/16 of an inch with a yellow tinge. Flour beetles are most voracious eaters during their larvae phase. Matured larva transform into cocooned pupa which is when flour beetles are most easily identified of their gender (we will see how to identify the sex of a flour beetle in a later post). From the pupa emerged the new adult beetle and the entire cycle from egg to adult takes around 6 weeks under optimal conditions.

Destructive (or dark) flour beetle pupa hatching to an adult

Let us first analyze the similarities and differences between the two most common flour beetle species: the red flour beetle and the confused flour beetle.

Red Flour Beetle (Tribolium castaneum) vs Confused Flour Beetle (Tribolium confusum)

Both species are nearly identical in physical composition. In fact, the “confused” flour beetle is named due to it being confused with the red flour beetle.

Both species are reddish-brown in color and about 1/8 of an inch in length. They leave in the same environments and compete for the same resources. The egg, larva, and pupa stages of both species are also very similar. The eggs are white, microscopic, and covered in sticky secretion with adheres flour bits. The larva phase has a creamy yellow color and two dark pointed projections at its posterior. The pupa is a lighter shade of yellow and looks similar to the Pokemon, Kakuna.

The defining differences between these two species is evident in their antenna. The antenna of the red flour beetle ends in a 3-segmented club and the sides of the thorax are slightly curved. The confused flour beetle has no apparent club on the 4-segmented antennae and the sides of the thorax are straighter. One additional distinction is that the red flour beetle may fly, especially before a storm, but the confused flour beetle does not fly.

Red flour beetle (left) and Confused flour beetle (right) | Purdue

Destructive flour beetle (Tribolium destructor), Mealworms (Tenebrio molitor), and Mini Mealworms (Tenebrio obscurus)

These three species are distinctive due to their dark-brown coloration.

The destructive flour beetle got its name due to the destructive damage it causes to stored grain products.

destructive or darkling flour beetle (Tribolium destructor)

Mealworms and its miniature sister species are high in protein content and makes them great food sources for reptile, fish, and bird pets.

Many cultures also consider mealworms to be delicacies and have even been incorporated into tequila-flavored novelty candies.

Tequila flavored mealworm (top) and mealworm-covered caramel apples (bottom)

Rebecca Baldwin and Thomas R. Fasulo. 2003. “Confused Flour Beetle, Tribolium confusum and Red Flour Beetle, Tribolium castaneum”. Entomology and Nematology Department, Institute of Food and Agricultural Sciences, University of Florida, Gainesville.

Dennis Calvin. 2001. “Entomological Notes”. Department of Entomology, College of Agricultural Sciences, The Pennsylvania State University.


Flour Beetles

The red flour beetle and confused flour beetle are cosmopolitan, secondary pests of stored grain. Adult beetles are 3 to 4 mm long, flattened, oblong, and chestnut brown. The head and upper parts of the thorax of the confused flour beetle are covered with minute punctures. The wing covers are ridged lengthwise and sparsely punctured between the ridges. Adults lay 450 minute, cylindrical, white eggs covered with a sticky secretion that become covered with flour or meal. Eggs hatch in five to twelve days. The yellowish-white, cylindrical grub is covered with fine hairs and is fully grown in twenty-seven to twenty-nine days. The pupa has no pupal case. Adults emerge in three to seven days. Depending on weather conditions, there may be four to seven generations a year, a generation developing in one to four months. Optimal conditions for development are 35o C and seventy percent relative humidity.

The sawtoothed grain beetle is a secondary stored grain pest. The adult is a slender, flat, brown beetle about 2.5 mm long. The thorax has six sawtooth-like projections on each side. The merchant grain beetle is a related species often confused with the sawtoothed grain beetle. Both species have similar biologies.


Sources of Information and Links

CABI. (2007). Tribolium castaneum (red flour beetle) datasheet. Crop Protection Compendium, 2007 Edition. CAB International Publishing. Wallingford, UK.

Dent D. (2000). Insect pest management.CAB International Wallingford, UK

Gaby, S. (1988) Natural crop protection in the tropics. Margraf Publishers Scientific books, Germany.

Infonet-biovision. http://www.infonet-biovision.org/default/ct/91/pests. Accessed on 28 Jan 2010.

Krischik, V.A., Cuperus G. and Galliart D. (1995). Stored Products Management, 2nd Edition, Oklahoma State Univ. 204 pp.

Mondal K. (1985). Response of Tribolium castaneum larvae to aggregation pheromone and quinones produced by adult conspecifics. International Pest Control, 27(3):64-66.

Mullen M.A. (1999). Special use pheromone -baited trap for the red flour beetle (Coleoptera: Tenebrionidae). Journal of Entomological Science, 34(4):497-500.

PaDIL – Plant Biosecurity Toolbox. Red rust flour beetle Tribolium castaneum . http://www.padil.gov.au/pbt. Accessed on 12 Jun 2011.

Venkataraman L.V. (1996). Repellence of callus derived pyrethrins to mosquito Culex quinquefasciatus Say and red flour beetle Tribolium castaneum Herbst. International Pest Control, 38(5):154-156, 159

Youdeowei A. (1993) Pest and vector management in the tropics. Longman group Ltd., England.


Confused Flour Beetle

Description: This 1/8 inch long, flattened, reddish brown beetle may appear somewhat shiny. The shield behind the head (pronotum) has minute punctures and the wing covers (elytra) are grooved (striate) with sparse punctures.

The most common relative to the confused flour beetle is the red flour beetle, Tribolium castaneum (Herbst), which can be even more abundant in the south. The biology and appearance is similar and the two species may occur together in stored food. The red flour beetle has the last three antennal segments enlarged abruptly and of equal size, but it lacks the notched expansion of the head behind the eyes and has the eyes farther apart than in the confused flour beetle. A number of other beetles and caterpillars also may infest stored products. Larger species (adults are almost ½ inch) of tenebrionid beetles, the yellow mealworm, Tenebrio molitor Linnaeus, and dark mealworm, T. obscurus Fabricius, are also occasional stored product pests, but they are probable better known because they are cultured and sold commercially as fish bait and pet food for reptiles, amphibians, and other insect feeders. Cylindrical, hardened, shiny, yellow or brown colored larvae (color is characteristic for the species), develop through 14 or 15 stages (instars) before pupating, producing one generation per year.

Life Cycle: Adult beetles are active and move about irregularly, hence the name. They can live for over a year. Eggs laid by females hatch in 5 to 12 days. Larvae are white, tinged with yellow, slender and cylindrical. They develop through 5 to 12 stages (instars) and grow to about 3/16 inch long over as few as 30 days. They have two short appendages on the end of the last abdominal segment. There may be 5 generations per year.

Habitat and Food Source(s): Mouthparts are for chewing. Found in stored food products like flour, cereals and other products (e.g., dried beans, peas, peppers and fruits, shelled nuts, spices chocolate, snuff, museum specimens and some drugs). Adults and larvae feed throughout stored food primarily in milled or prepared products. They are perhaps the most common pest of processed flour. This species is often used as a test animal in laboratory experiments because it is easy to keep in culture.

Pest Status: Found world-wide infesting stored food infestation may affect flavor of product medically harmless, even if ingested.

For additional information, contact your local Texas A&M AgriLife Extension Service agent or search for other state Extension offices.

Confused flour beetle, Tribolium confusum Jacquelin du Val (Coleoptera: Tenebrionidae). Photo by H. A. Turney. Yellow mealworm, Tenebrio molitor Linnaeus, (Coleoptera: Tenebrionidae), larva, pupa and adult. Photo by Drees. A tenebrionid, Lobopoda sp. (Coleoptera: Tenebrionidae). Photo by Jackman. A tenebrionid, Eleodes sp. (Coleoptera: Tenebrionidae). Photo by Jackman.

Literature: Ebeling 1978 Metcalf et al. 1962 Swan & Papp 1972.


Fungi species and red flour beetle in stored wheat flour under Jazan region conditions

Infection of stored wheat flour with insects and toxic fungi can be an extremely serious problem. This study was conducted to isolate and identify the fungal species and insects in different stages, which infested and contaminated the stored flour under Jazan region conditions and changed its color and flavor. The obtained results revealed that the isolated insect was the red flour beetle Tribolium castaneum. Live adult, larvae and cast skin were isolated. Four Aspergillus species were isolated from stored wheat flour the isolated species prevalence being A. flavus > A. niveus > A. terreus > A. niger by rate 44.5%, 37.8%, 10.9% and 6.7%, respectively. The same fungal species isolated from flour were also isolated from different insect stages. A. flavus was the most common fungus and A. niger was isolated with a lower rate. The results about the isolated fungi either from the suspension of adult insects, larvae or cast skins may confirm the role of T. castaneum to carry and distribute fungi in different parts of the stored flour.

Keywords: Aspergillus species Jazan Wheat red flour beetle stored wheat flour.


Ancient Egyptians weakened beetles’ water balance using stones

The new study, as well as a previous study, also conducted by Kenneth Veland Halberg, demonstrates that beetles solve the task of regulating their water and salt balance in a fundamentally different way than other insects. This difference in insect biology is an important detail when seeking to combat certain species while leaving their neighbors alone.

“Today’s insecticides go in and paralyze an insect’s nervous system. The problem with this approach is that insect nervous systems are quite similar across species. Using these insecticides leads to the killing of bees and other beneficial field insects, and harms other living organisms,” explains Kenneth Veland Halberg.

The centrality to survival of the carefully controlled water balance of beetles is no secret. In fact, ancient Egyptians already knew to mix pebbles in grain stores to fight these pests. Stones scratched away the waxy outer layer of beetles’ exoskeletons which serves to minimize fluid evaporation.

“Never mind that they chipped an occasional tooth on the pebbles, the Egyptians could see that the scratches killed some of the beetles due to the fluid loss caused by damage to the waxy layer. However, they lacked the physiological knowledge that we have now,” says Kenneth Veland Halberg.


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