A tropical lady beetle, Diomus lupusapudoves (Coleoptera: Coccinellidae), deceives potential enemies to predate an ant-protected coffee pest through putative chemical mimicry

Abstract

Several beetle species in the family Coccinellidae have evolved close associations with ants in order to consume ant-tended hemipteran prey. These myrmecophilous lady beetles employ various strategies for avoiding ant aggression, including physical and chemical protection. We asked how the lady beetle Diomus lupusapudoves Vandenberg, Iverson and Liere (Coccinellidae: Diomini) is capable of avoiding ant aggression in a Mexican coffee agroecosystem, given that its larvae are physically unprotected from the aggressive Azteca sericeasur Longino (Formicidae: Leptomyrmecini) ants. Through a classic scale-ant mutualism, these ants protect the primary food source of D. lupusapudoves, the green coffee scale, Coccus viridis Green (Coccidae: Coccini), an agricultural pest of coffee. Through three quantitative behavioral lab experiments, we found that the ants did not show aggression towards either D. lupusapudoves larvae or towards C. viridis. Similarly, the ants were not antagonistic to crickets (Orthoptera), which normally induce aggression, when they were covered in a coating of D. lupusapudoves larvae residues. Through a survival analysis, we found that D. lupusapudoves larvae are not apparently toxic to the ants, as ants that consumed a sugar solution containing the D. lupusapudoves larvae lived longer than those fed only a control sugar solution. From these series of experiments, we deduce that the D. lupusapudoves larvae likely employ chemical mimicry, allowing them to coexist with the aggressive A. sericeasur ants. The myrmecophilous behavior of the D. lupusapudoves larvae assists them in their role as an important biological control agent of the green coffee scale.