The aim of this study was to comparatively characterize the monthly variation and the sex ratio of Euxesta stigmatias (Loew) and Euxesta sororcula (Wiedermann) populations from a natural reserve and from a guava orchard. It was also investigated whether density and the climate factors affected the individuals' size and fluctuating asymmetry (FA). In both environments, E. sororcula predominated over E. stigmatias. The number of individuals of E. sororcula collected in the ecological station was significantly lower than the number of individuals caught in the orchard. However, the number of captured individuals of E. stigmatias did not differ between environments. Significant sex ratio differences were detected between the collection sites. Female's frequency of E. stigmatias was significantly higher than male's frequency in the ecological station, but not in the orchard. An opposite pattern was encountered for E. sororcula population, showing a significant larger number of females only in the orchard. The species populations also differed in the degree of asymmetry presented. Euxesta stigmatias individuals showed no change on size or on FA along the captures and between environments. Moreover, E. sororcula tended to be more susceptible to climatic variations, considering the significant observed correlation between temperature and body size and the expressive body size and FA variations. This study illustrates the influence of the environment in some structural and dynamic parameters of the studied populations.

This study analyses the role of body size and symmetry in the sexual selection and courtship behavior of Dysdercus maurus Distant. Sexual conflicts signaled by coercive mating, female resistance, and pre-copulation fights illustrate the mating system. Male-female struggles were observed in all mating attempts. Females tried to reject males by pushing or running and even by vigorously shaking their bodies, in attempts to dislodge the male from their dorsum. In spite of sexual conflicts during courtship, females actively chose their mates based on morphological and behavioral traits. Larger males with more symmetrical tibiae and longer tarsi that are better copula imposers were more successful in sexual competition. Evidence is presented that sexual conflict and female mate choice should not be mutually excluded.