June 14, 2011

In many arthropod species, males provide females with a gift during mating. This “nuptial gift” gives the females nutrition that helps them live longer and produce more offspring, but during mating the males of some species can cause significant physical damage to the females.  

Charles Fox, entomology professor in the University of Kentucky College of Agriculture, conducted research to discover if females use these gifts as a source of food and thus “forage” for males when they are hungry. He did this by asking how female dietary changes affect the female cowpea weevil’s mating rate, lifespan, physical health and number of offspring.

The cowpea weevil is a beetle and a significant pest in tropical areas and in stored legumes, an environment in which the adult beetles generally have no access to food or water.

“The beetles are an important model system for reproductive biology and sexual selection,” Fox said. “We do basic science in which we try to understand how different kinds of stress influence insect behavior and life history.”

His research publication on this subject was named the best paper in the past two years of the Royal Entomology Society’s Physiological Entomology Journal published in London, England. The award was chosen by the journal’s editors.

Through his research, Fox gave female weevils that had already mated once access to water, sugar water, yeast or nothing at all. He found that when given water, female weevils experienced less weight loss, had a slightly longer lifespan and produced a few more offspring than unfed females. Those given sugar water had more offspring and lived longer than those only given water. Beetles given just yeast had no positive effects on offspring numbers or life span. This demonstrated that lack of water or sugar reduced the health of female beetles.

Females without access to food or water—those that should be hungry—were more receptive to mating than those fed sugar or water. Those given water were the next likely to mate again, while beetles given sugar were the least likely to remate and likely would go longer between mating than the other two.

“Our work demonstrates that mating behavior of some insects, including their tendency to mate multiple times despite physical harm experienced during mating, may evolve as a means to obtain resources needed for reproduction,” Fox said.

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