ARS | Publication request: Effects of flour conditioning on cannibalism of T. castaneum eggs and pupae

Submitted to: Environmental Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 2, 2012
Publication Date: December 17, 2012
Citation: Flinn, P.W., Campbell, J.F. 2012. Effects of flour conditioning on cannibalism of T. castaneum eggs and pupae. Environmental Entomology. 41(6): 1501-1504. http://dx.doi.org/10.1603/EN12222.

Interpretive Summary: The red flour beetle is a serious pest of flour mills and stored grain. Cannibalism by adult and larval red flour beetles of eggs and pupae can have important implications in population regulation. As the red flour beetles develop, the flour becomes conditioned. This is due to an accumulation of beetle feces, chemicals produced by the beetles, and nutritional depletion of the flour. There is a need to understand how different levels of flour conditioning affect the rate of cannibalism of the red flour beetle. We found that larvae had the highest rates of egg and pupal cannibalism, followed by adult females. Adult males had the lowest rates of cannibalism. Cannibalism of eggs by female adults was highest in fresh flour, and decreased with the amount of flour conditioning. The level of flour conditioning had no affect on rates of cannibalism by larvae or adult males. These results will enable scientists to develop an improved computer model for the red flour beetle, which can be used to predict insect outbreaks and develop better insect pest management recommendations.

Technical Abstract: Cannibalism is a very important factor regulating population dynamics of the red flour beetle. After several days of feeding, the flour becomes conditioned by the beetles, which can affect rates of cannibalism. Flour conditioning is caused by an accumulation of feces, pheromones, and ethylquinone, which is a repellent produced by the beetles. We determined the effect of five different levels of flour conditioning on cannibalism of red flour beetle eggs and pupae by adult and larval stages. Larvae had the highest rates of egg cannibalism (12 eggs eaten over the 4-day period) followed by female adults (7 eggs consumed). Adult males had the lowest rates of cannibalism with only 2 eggs consumed. Cannibalism of eggs by females was negatively correlated with the level of flour conditioning. There was no effect of flour conditioning on egg or pupal cannibalism by larvae or adult males. Cannibalism by adult females may decrease as the level of flour conditioning increases because females may spend less time tunneling in highly conditioned flour and more time trying to disperse to other areas that are better for oviposition.