The influence of male dominance in female Anastrepha curvicauda mate selection

Chemosensory input from mouthparts in response to sexually dimorphic cuticular wax mediates male sexual discrimination in Galerucella grisescens (Coleoptera: Chrysomelidae)

The surface of the insect body is covered with a hydrophobic layer called cuticular wax (CW). In addition to functioning as an anti-desiccation agent, CW is critical for chemical communication. It has been reported that in Chrysomelidae, males discriminate between sexes based on the sex-specific CW. However, little is known regarding the underlying sensory basis. Herein, we demonstrate that chemosensory input from mouthparts mediates sexual discrimination in male Galerucella grisescens (Chrysomelidae). Observations of mating behaviour, bioassays for CW, and chemical analyses revealed that G. grisescens possess qualitatively sexually dimorphic CW, and such compositional differences allow males to distinguish between sexes. Using electron microscopy, blocking male chemosensory organs, and electrophysiological experiments, we showed that male mouthparts bear chemosensory sensilla tuned to female CW components, and sensory input from them induces male aedeagal insertion, a common male behavioural response to females. Thus, detecting CW via mouthparts is essential for males to distinguish between sexes, consistent with the fact that males inspect conspecific individuals by licking their body surfaces. To our best knowledge, this is the first report describing the detailed functional roles of mouthparts in sexual discrimination in Coleoptera. We believe that this study will promote further studies on insect chemical communication.

Mate Selection on Anastrepha curvicauda: Effect of Weight, Age, and Virginity

Sexual selection determines the evolution of the species by favoring some attributes that confer a reproductive advantage to those individuals with those attributes. Tephritidae flies do not always select the same traits when looking for a mating partner. Some aspects of the mating system of Anastrepha curvicauda are known; nevertheless, there is no information on the effect of age, size, and virginity when selecting a mating partner. We set up a series of experiments where a selector (male or female) may select between (a) an old or young partner, (b) a small or large partner, and (c) a virgin or mated partner. Males of A. curvicauda significantly preferred large, young, and virgin females, while females showed no preference for high- or low-quality males. The females' non-preference for a particular male is discussed in the light of their mating system.