Red flour beetle

Adult

Adult beetles are small, around 3–4 mm long (1/8 inches), of a uniform rust, brown or black color.[2] Head and pronotum are sometimes darker than rest of body.

The red flour beetle attacks stored grain and other food products including flour, cereals, pasta, biscuits, beans, and nuts, causing loss and damage. The United Nations, in a recent post-harvest compendium, estimated that Tribolium castaneum and Tribolium confusum, the confused flour beetle, are "the two most common secondary pests of all plant commodities in store throughout the world."[3] A research on Hermetic storage of wheat and maize flour protects against red flour beetle (2017) was conducted that found 12 days under hermetic storage results in 100% RFB mortality and confirms that hermetic environments are sufficient for controlling insect pests.[4]

Tribolium castaneum as shown under the microscope

The red flour beetle is of Indo-Australian origin and less able to survive outdoors than the closely related species Tribolium confusum. It has, as a consequence, a more southern distribution, though both species are worldwide in heated environments. The adult is long-lived, sometimes living more than three years. Although previously regarded as a relatively sedentary insect, it has been shown in molecular and ecological research to disperse considerable distances by flight.[5]

Female red flour beetles exhibit polyandrous mating behavior. Within a single copulation period, a female will mate with multiple males. Any one male may have a low sperm count, having depleted its supply through prior matings, so mating with several increases the female's likelihood of obtaining an adequate amount of sperm.[6]

Polygamy in red flour beetles is a behavior common to both males and females of this species. Polyandry is thus polygamy in the female members of a population as discussed in the section above. On the other hand, polygyny refers to polygamy practiced by males in a population.

In red flour beetles, males are known to engage in polygamous behavior. Research largely shows that Male red flour beetles engage in polygamous behavior to avoid inbreeding depression, especially when there is competition from other males. There is a higher fertilization success in out-bred males when they compete with inbred males to fertilize the same female.[15]

In polygamous beetles, the male that last fertilizes the female ends up having a higher fertilization success. Polygamy can thus be seen as an evolutionary result as males compete to be the last to fertilize the female's egg and contribute more to the next generation. Sperm precedence is thus a means of evolutionary competition through which the males try to achieve greater reproductive success.[16]

The Red Flour beetle has played an important role as a model organism serving as a model for development and functional genomics. Compared to Drosophila, the Red Flour beetle more closely represents the development of other insects.[17] In 2008, the genome of Tribolium castaneum was sequenced, analyzed, and compared to other organisms such as Drosophila. The Red flour beetle and the fruit fly share about 10,000-15,000 genes. Despite their shared genes, they do have their differences. During development, anterior-posterior patterning is normally regulated by the bicoid gene in Drosophila. However, in the Red Flour beetle, there is no bicoid orthologue, but instead the genes orthodenticle and hunchback substitute for bicoid in anterior patterning.[17]

Red Flour beetles are particularly useful for doing RNAi (RNA interference) experiments. RNAi is RNA that degrades mRNA transcripts to show a knock-down of gene function. Compared to in Drosophila, RNAi has a greater response in the Red Flour beetle, making it ideal for knock-down experiments.[18]

CRISPR technology has been shown to be useful in studying Tribolium castaneum. In one experiment, researchers used CRISPR to knock out the E-cadherin gene. E-cadherin is a membrane bound protein of epithelial cells involved in cell-cell adhesion.[19] This resulted in developmental issues in dorsal closure. RNAi knock-down of E-cadherin shows the same effect.[20] This shows that CRISPR technology and gene editing are viable options for studying the Red Flour beetle as an insect model organism.

Synonyms of Tribolium castaneum (Herbst) are:[21][22]

• Colydium castaneum Herbst, 1787
• Margus castaneus Dejean, 1833
• Phaleria castanca Gyllenhal, 1810
• Stene ferruginea Westwood, 1839
• Tenebrio castaneus Schönherr, 1806
• Tribolium ferrugineum , Wollaston, 1854
• Tribolium navale (Fabricius, 1775)
• Uloma ferruginea Dejean, 1821

The following names have been cited as synonyms of T. castaneum by some authors but they actually refer to other species:[21]

• Dermestes navalis Fabricius, 1775
• Ips cinnamomea Herbst, 1792
• Ips testacea Fabricius, 1798
• Lyctus navalis (Fabricius, 1775)
• Margus ferrugineus Kuster, 1847
• Stene ferruginea Stephens, 1832
• Tenebrio bifoveolatus Duftschmid, 1812
• Tenebrio ferrugineus Fabricius, 1781
• Tenebrio ochraceous Melsheimer, 1806
• Trogosita ferruginea (Fabricius, 1781)
• Uloma ochracea
• Uloma rubens Dejean, 1836

• Flour beetle
• Home stored product entomology

• Granousky, T. A. 1997. "Stored Product Pests". In: Handbook of Pest Control, 8th Ed. Hedges, S.A. and D. Moreland (editors). Mallis Handbook and Technical Training Company.

Wikispecies has information related to Tribolium castaneum.

• Tribolium castaneum genome. Archived 2016-03-01 at the Wayback Machine Beetlebase.
• Tribolium species comparison.
• Confused and red flour beetles. University of Florida IFAS.
• Cattlin, Nigel. "Rust Red Flour Beetle". Bayer Crop Science UK. Retrieved 2021-03-08.