A Sex Pheromone in the Desert Tenebrionid Beetle Parastizopus armaticeps

Abstract

Males of the desert beetle Parastizopus armaticeps (Pér.) (Coleoptera: Tenebrionidae) exhibit a characteristic calling behavior that attracts females by raising the tip of the abdomen, exposing the aedeagus, and remaining in this posture for a few seconds while emitting a pheromone. We collected the pheromone by holding a solid phase microextraction fiber (100 mum polydimethylsiloxane) close to the aedeagus for 5 s and analyzed the volatiles collected by gas chromatography/mass spectrometry. The volatiles consisted of 3-methylphenol (52%), ethyl-1,4-benzoquinone (48%), and 3-ethylphenol (2%). The pheromone originated from the aedeagal glands. In the gland reservoirs, these compounds (2.1%) were mixed with ethyl, isopropyl, and propyl esters of fatty acids (24.2%), and a mixture of hydrocarbons (69.1%). The mean amount of volatiles extracted from gland reservoirs was 0.92 +/- 0.83 microg. Chemo-orientation experiments with a servosphere show that females responded only to the ternary volatile mixture. Females stopped walking, elevated the front parts of their bodies with erected antennae, turned slowly on their own axis, and walked upwind toward the odor source. Single components or binary mixtures did not elicit responses from females. Males did not respond to the pheromone. Evolutionary aspects of this pheromone system are discussed.