Comportamento sexual da vespa escavadora Sphex ingens Smith 1856 (Hymenoptera, Sphecidae)

Abstract

Wasps of the genus Sphex ingens (commonly known as digger wasps) are widely distributed in Bahia and in Brazil’s southeast Atlantic coast, representing a poorly understood species in terms of behavior, ecology and biology. The present study aims to describe the sexual behaviour in natura of the species, as well as to evaluate behavioral strategies and morphological patterns subject to sexual selection. The study was conducted on Meros and Aventureiro beaches, between the 2nd fortnight of 2010 and the 1st and 2nd fortnights of 2011, using tabulation and footage of the mating behaviors of individuals in both faces. The ethogram was developed using ad libitum and sequence samples methods. Flow diagrams were drawn based on the current state and on the stochastic probabilities of the behaviors. The mating was composed of four sequential steps of a promiscuous mating system. There were 10 types of behavior which were exclusive to females and 9 other types which were exclusive of males. Seven behaviors were common between the sexes, with no significant difference (x2=16,622; Gl=n-1; p<0,01). Communication behaviors were more frequent between the sexes during the mating process, however, the recorded predictions in the Markov chain diagram indicated that these behaviors have little influence on mating, being the males’ permanency and the females’ agonistic & intractability behaviors much more relevant. The number of attempted copulations between patrol and resident males were significantly different in the 2nd fortnight of 2010 and 1st fortnight of 2011, respectively, t=3,767; n=Gl-1; p<0,01 and t=12,780; Gl=n-1, p<0,01. Although no significant differences existed for the quantities of mating between patrol x residents males in the 2nd fortnight of 2011 (t=0,285, Gl=n-1, p<0,01), the results suggest that the copulatory success between these patterns is variable along the reproductive season. The number of touches on each other antennas and the investment time between successful x unsuccessful mating were significantly correlated (rs=0,838; t=14,127, p<0,001 and rs=0,847; t=14,083; p<0,001), however, the number of antennas touches occurring between successful x unsuccessful copulations did not differ significantly (t=0,607; Gl=n-1; p<0,01), unlike the investment period between the matings (t=4,236; Gl=n-1; p<0,01). A variance analysis demonstrated significant differences in measured morphological traits, while a multivariate analysis predicted an asymmetry between females, patrol males and resident males. The asymmetry between resident and trooper males indicates a greater adaptation to the territorialism than the females selection for this pattern. Meanwhile, the females aggression and promiscuity may interfere on the males' courtship behaviour and fosters the development of copulatory coercivity.