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Male cricket songs spark more socializing among female crickets, study finds

Within the last decade or two, the vast majority of Hawaiian field crickets (Teleogryllus oceanicus) have lost the ability to create their mating song due to a mutation affecting the male crickets' wings. This mutation, referred to as "flatwing," has been overall beneficial for the crickets, keeping them safe from a parasitic fly that finds them by listening to their song. However, scientists are interested in how the rapid spread of this mutation has affected the crickets' social dynamics.

Most prior research has focused on the male-male or male-female interactions of these crickets, mostly to observe mating patterns and aggression between males. Little research has focused on interactions between female crickets. But a new study, in the journal Proceedings of the Royal Society B, sheds some light on the female-female interactions and how they differ when male song is present.

The flatwing mutation is also present in female crickets, but only affects the wings of males. To get a fuller understanding of how the gene might affect social dynamics, the researchers used both female crickets that carried the mutation and those that didn't. During the experiment, researchers placed females of either matching or mismatching genotypes in arenas in pairs of two, then exposed them to either male song or silence. In total, they conducted 167 trials with 334 different female crickets and recorded their interactions.

Overall, the crickets interacted frequently, but interactions were more frequent and lasted longer in the presence of male song. The authors explain, "Intrasexual female social behavior was common, expressed by 86.5% of individuals. Females primarily engaged in antennal contact, which is reasonable to interpret as detection and assessment behavior. Antennal contact increased in the presence of song, in terms of how likely females were to do it, how many times they did it, and for how long."

The pairs that had similar genotypes (flatwing-flatwing, normal wing-normal wing) interacted more on average than the mixed groups, but all group combinations increased interactions when male song was played.

Five different behaviors were observed in the trials: antennal contact, mounting, acceptance of mounting, biting, and flight attempts. Antennal contact was the most frequent interaction by far, followed by biting, which is considered an aggressive interaction. Only 27 of the crickets attempted to fly away, and most of these attempts took place in the absence of song.

Only two instances of mounting occurred in the study, but the behavior was only accepted by the other cricket in one of the two cases. The researchers note that this behavior had not been previously observed, but that was likely due to a lack of female–female observations in general.

The findings of the study raise some questions about the impact of the flatwing mutation, and highlight the importance of studying interactions between both sexes, especially when rapid evolutionary changes take place.

"The reproductive success of flatwing males is inherently tied to female mate choice, which has been suggested to potentially be a stronger factor than flatwing satellite behavior in reducing parasitism risk. It is therefore possible that female–female social behaviors indirectly influence parasitism risk, though this requires further study," the study authors write.