Studies on a sexual pheromone or Planococcus citri (Risso) (Homoptera, coccoidea). II. Extraction.
In this second part of a series of studies on the sex pheromone produced by the females of Planococcus citri (Risso) [cf. RAE/A 63, 1167], the testing of techniques for extracting this substance is described. Crushed and intact virgin and mated females were immersed in water, ethanol, diethyl ether, acetone, glacial acetic acid, toluene, petroleum ether, methylene chloride, n-hexane or pentane, and also two absorbent layers of silica substrate were used to enclose and absorb the attractant from an intervening layer of virgin females. The preparations were tested on discs of filter paper, paraffin wax and hydrophilous poly(methyl methacrylate) in petri dishes containing virgin males. The ethyl-alcohol, diethyl-ether and petroleum-ether preparations of uncrushed virgin females were attractive to the males, and ethanol preparations from immersed or stratified females placed on filter-paper or hydrophilous poly(methyl methacrylate) provoked the highest number of mating attempts. The preparations were still attractive after refrigeration for more than a week. The results with mated females were erratic.