Environmental and pheromonal control of precopulatory behavior for synchronized mating in the white grub beetle, Dasylepida ishigakiensis (Coleoptera: Scarabaeidae)

Abstract

Precopulatory behavior of the white grub beetle, Dasylepida ishigakiensis, was observed under laboratory conditions to determine the environmental factors controlling mating behavior, which is synchronized among individuals at dusk in the field. When light intensity was gradually decreased, both females and males sequentially started moving their antennae, legs and abdomen, then walking, and females rhythmically extruded their abdomen while males opened the elytra to fly. Pheromone release by females was suggested in a wind tunnel assay in which males oriented themselves to both intact and crushed bodies of females, but not of males. When illumination was suddenly turned off, precopulatory behavior of females and males was similarly induced but the frequencies of calling and flying behaviors were significantly reduced as compared with those observed when light intensity was gradually reduced. This result may suggest that gradual darkening is an important factor for their synchronized appearance from the soil and subsequent mating behaviors, including pheromone release in females and orientation flight in males. These behaviors were significantly suppressed at low temperatures below 18°C. This result supports our previous conclusion that temperature is the primary factor controlling the emergence and mating activity of sexually mature beetles in the field.