Mating behaviour of the large-head resin bee Heriades truncorum (Megachilidae: Osminii) suggests female plastic strategy in selection of a mating partner and male quality assessment

Behavioural courtship display and size of males are two attributes often used by females to select a mating partner. According to sexual selection, such traits are of importance, because a bigger size male or males displaying a better courtship could enhance the possibility of females to transmit her genes to the following generations via her offspring. In Hymenoptera such as in solitary bees, it is known that females can assess male quality and add this information in the process of mating choice. In the current study, I describe aspects of pre-copulatory mating behaviour of males, male quality assessment and female choice in the large-headed resin bee Heriades truncorum (Hymenoptera: Megachilidae: Osminii). Males of Heriades truncorum perform thoracic vibration, fan their wings and lift upwards female's abdomen to copulate. Couples engage in sideways rocking motion movement like a dance. Female selection of a partner was also found to be density dependent. In a pair situation (one female for one male), female copulate equally with males of all sizes and male mating effort enhanced the chance of successful copulation. In an environment with mating choices (one female for two males of different sizes), successful copulation was significantly more frequent for bigger size males. Female response to male mounting took place independently of the number of mating partners in the arena and did not impair mating. Additionally, size had no effect on male-male competition. Both results suggest mating success in Heriades truncorum rely on a female choice mechanism.

Automated summary

Behavioural courtship display and male size are important factors in mate selection for females. In the case of the large-headed resin bee, females can assess male quality and choose a suitable mate. Male mating behaviour involves vibration, wing fanning, and lifting the female's abdomen for copulation. Female preference for a male partner is density dependent and mating success is influenced by male size. Female response to mounting is independent of the number of mating partners and does not affect the mating process. These findings suggest that female choice plays a significant role in mating success in the large-headed resin bee.