A unique form of "pheromonal chorusing" was discovered in females of the arctiid moth Utetheisa ornatrix. Female moths have been known as one-way "signalers" transferring advertisement pheromone to male "receivers", however, the intrasexual perception and interactions have generally been ignored. Despite the previous studies, recent evidence from neurophysiology suggests that some female moths, including U. ornatrix, do have the ability to perceive conspecific female-produced pheromone. I investigated this question from a behavioral perspective. Female U. ornatrix begin to release advertisement pheromone ('calling') after the onset of darkness. The calling is characterized by rhythmic extrusion of the abdominal tip, bearing the pheromone glands. I observed calling females in two social arrangements: grouped six (GRP) and solitary females (SOL). These situations influenced their calling behavior. GRP began their calling in a shorter time period than SOL. Once an individual initiated calling, following calls in GRP began earlier than SOL. The calling frequency (calculated by the number of ovipositor extrusions per minute) of GRP was higher than that of SOL, and the former also increased faster than the latter for the first calling hour. There was a higher incidence of calling in GRP and the proportion of calling individuals increased faster in GRP than in SOL. These results suggest that female U. ornatrix perceived the conspecific female pheromone and responded to it by controlling their call timing and frequency. This behavior may be interpreted as intrasexual competition in which females seek to appear more attractive to males than neighboring females.
Species 1: Lepidoptera Arctiidae Utetheisa ornatrix (ornate moth)
Keywords: ovipositior extrusion frequency, grouped female calling
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