Male Ventroposterior Brush Display Increases the Sexual Receptivity of Females in the Gregarious Beet Webworm Loxostege sticticalis (Lepidoptera: Crambidae)

Abstract

Males of many moths possess scent organs, ranging from simple scales and hair-tufts to complex glands. Males of the gregarious beet webworm Loxostege sticticalis (Lepidoptera: Crambidae) display their ventroposterior brushes (VPBs), located on the eighth abdominal sternite, toward adjacent females and usually maintain this posture until sexually receptive females become available, or the arrival of photophase. The peak period of male L. sticticalis VPB display during the scotophase broadly coincides with that of mating. Our experiments revealed that females exposed to male VPB display increased their calling behavior and were more likely to mate than those exposed to males that did not display their VPBs. Volatile chemicals provide the only reliable sensory modality for intersexual communication in L. sticticalis because all behavioral assays were conducted in a sealed darkroom, thereby eliminating a role for visual signals, and no vibratory signals occurred during VPB displaying. Therefore, odors released from the VPB of male L. sticticalis may act as aphrodisiac signals to conspecific females in order to enhance female receptivity and increase his mating success. Our study indicates that chemical communication in these gregarious moths apparently involves mutually stimulating interactions between female attractant and male courtship pheromones.