Male-Specific Substances Possibly Contributing to Nuptial Flight of the Japanese Carpenter Ant Camponotus Japonicus (Hymenoptera: Formicidae)

The nuptial flight of ants usually occurs during certain periods of the year. Alate females and males fly out of their nests to mate simultaneously. In the genus Camponotus , sex-specific chemicals are deposited in the male head capsule; however, their roles in nuptial flight have not yet been clarified. This study aimed to elucidate the functions of male-specific chemicals in the Japanese carpenter Camponotus japonicus . First, we identified three chemicals attributed to the male as authentic chemicals: methyl salicylate (MS), methyl 6-methyl salicylate (MMS), and methyl anthranilate (MA). Electroantennogram (EAG) responses to these three chemicals were confirmed to occur in male and female alates. Subsequently, the amounts of MMS and MA in the alate male head capsule were compared before and after flight under laboratory conditions. The amounts of both substances were significantly reduced after flight, suggesting that males secreted these substances during flight. Thereafter, a field trap experiment was conducted in three fields of the Kyoto Prefecture during the nuptial flight season in 2021 using MMS and MA as bites. The number of captured alate males was significantly higher than that of the females, suggesting that these compounds primarily attracted males rather than females. Considering the field conditions, if the local concentration of these chemicals is increased by male aggregation, females may be attracted because EAG responses were also observed in females. Our findings represent a first step toward understanding chemically mediated male lek formation during the process of male aggregation syndrome in this species.