A Two-Component Female-Produced Pheromone of the Spider Pholcus beijingensis

Chemical signaling plays an important role in spider sexual communication, yet the chemistry of spider sex pheromones remains poorly understood. Unlike insects and mammals, the identification of spider pheromones has seldom been attempted, and no multicomponent pheromones have been found. Empty webs of sexually receptive females of Pholcus beijingensis were more attractive to male conspecifics as compared to webs of sexually unreceptive females or to mature males. Coincidently, chemical analysis revealed that (E,E)-farnesyl acetate, diisobutyl phthalate, and hexadecyl acetate of the spider webs exhibited higher relative abundances in sexually receptive females than in sexually unreceptive females or males, indicative of possible pheromone components. Two-choice behavioral assays verified that the blend of (E,E)-farnesyl acetate and hexadecyl acetate (w/w: 2:1) attracted males at a dosage equivalent to the amounts of these compounds in one spider web, whereas neither compound alone aroused males. In addition, diisobutyl phthalate (a likely contaminant from contact with plastic) alone or in combination with either of the acetates did not evoke the males' attraction. The behavioral data suggest that (E,E)-farnesyl acetate and hexadecyl acetate comprise a two-component female-produced sex pheromone in P. beijingensis, the first multicomponent pheromone found in spiders.