Brooding Behavior in Elasmucha putoni (Heteroptera : Acanthosomatidae), and a Possible Nymphal Alarm Substance Triggering Guarding Responses

Abstract

E. putoni females straddled their eggs and nymphs and showed specific defensive behavior when disturbed. Females usually returned to egg masses after being separated from them, but could not discriminate their own eggs from others. When exposed to a crushed nymph, females showed intense defensive behavior (e.g. wing fanning) more frequently than when they were exposed to a control (forceps). In contrast, both E. putoni and E. dorsalis (a closely related subsocial species) females with amputated antennae showed the same reaction to crushed nymphs as control females. In both species, aggressive behavior was also triggered by crushed nymphs of related subsocial or asocial species. These results strongly suggest that the odor released from injured nymphs functioned as an alarm substance triggering maternal defensive responses. The substance is probably common in acanthosomatid bugs regardless of presence or absence of parental care. The adaptive significance and evolutionary origin of the smell-mediated alarm system in offspring-parent interrelations are discussed.