The expression of aggression in the dobsonflies Corydalus magnus Contreras-Ramos, 1998 and Platyneuromus soror (Hagen, 1861) (Megaloptera: Corydalidae)

摘要

The expression of aggression in Megaloptera has received little attention, specifically for the adults of the subfamily Corydalinae. Among the New World species of Corydalinae, it is not known if aggression is triggered and expressed in the same way. Since two genera, Corydalus Latreille, 1802 and Platyneuromus Weele, 1909 have different courtship strategies, the effect of the social environment in the expression of aggression in two species of those genera, Corydalus magnus Contreras-Ramos, 1998 and Platyneuromus soror (Hagen, 1861), is examined here and compared with the known data in Corydalus bidenticulatus Contreras-Ramos, 1998. Our results suggest that the triggering of aggressive behaviours in the three species is similar. The decision of whether or not to fight is affected by their social environment: a male is aggressive against other males only when a female is present. Furthermore, the intensity of aggression does not differ among the three species. The behavioural observations support the idea that the mandibles of Corydalus males are used as weapons in male-male competition and during the courtship, but the post-ocular flanges of P. soror males are not involved in male-male competition (they use their short mandibles to bite). Conversely, data show that such a feature might act as a signal trait for female choice.