Imported Fire Ants Discard cricket eggs

Abstract

The house cricket, Acheta domesticus (Linnaeus), is often used as a food source for maintaining imported fire ants in laboratory culture. It was found that both red imported fire ants, Solenopsis invicta Neighbors, and black imported fire ants, S. Richteri Trout consumed most of the soft tissues of female crickets, but avoided their eggs by throwing them into waste piles. Bioassays with freshly collected cricket eggs showed that ants first collected the eggs from their nests and then threw them into the waste piles. The main chemicals on the surface of cricket eggs were found to be fatty acids, including lauric acid, myristic acid, palmitoleic acid, palmitic acid, linoleic acid, oleic acid and stearic acid. Fatty acids are known death signals in insects and inducers of widespread necrophoric behavior in ants. It was shown that both the cricket egg extract and the reconstructed fatty acid mixture elicit the necrophoric behavior St. Invincible; however, they never elicited retrieving behavior. Unknown chemicals on cricket eggs, other than fatty acids, may be responsible for the retrieving behavior. Interestingly, cricket eggs had a fatty acid profile very similar to that of dead ants collected from waste piles. Possible causes for such a close match in fatty acid profiles between dead ants and cricket eggs are discussed.