Size Matters - Correlation of Body Size, Structure of Sternal Glands and Mating Success in Echinothrips Americanus (Thysanoptera: Thripidae)

Females of many insect species analyse and select specific male signals for possible mates. Mate choice can benefit fecundity and survival of females, or have an indirect effect by providing optimal genes. Assortative mating by size is one of the most commonly observed sexual behaviors. Additionally, chemical cues may be detected by females, as these can also be indicators of body size and condition. Little is known about mate choice behavior among Thysanoptera. The mating system of Echinothrips americanus (Thysanoptera, Thripidae) is characterized by a strong competition for mates, leading to assortative mating. In this species very prominent gland structures are located on sternites III to VIII, of which the function still remains unknown. However, given the individual differences in expression of the gland release areas, a probable role in mate selection is postulated. In this study, we are interested in possible correlations between male body size, gland release areas, glandular substances, and mating success. Additionally, we used an experimental approach to test for a possible function in mate-assessment, or as an anti-aphrodisiac. Whereas pronotum length, distance between 1st and 2nd coxa, as well as total sternite area show a significant correlation with mating success, no direct correlation with sternal gland structures was observed. Furthermore, we failed to constitute a mate-assessment or anti-aphrodisiac-like function of sternal gland products.