SEMIOCHEMISTRY OF APOSEMATIC SEED BUGS

Jeffrey R. Aldrich¹, Walter S. Leal² and RitsuoNishida^3
1USDA/ARS, Insect Chemical Ecology Lab., B-007, BARC-West,Beltsville, MD USA 20705.
²National Institute of Sericultural & Entomol. Science,Ibaraki 305, Japan.
³Pesticide Research Institute, Kyoto University, Kyoto 606,Japan.

(E)-2,7-Octadienyl acetate and (E)-2-octenyl acetate (1:10 by volume)were identified as a pheromone attractive to both sexes of the lygaeidbug, Tropidothorax belogolowi. In a parallel investigationof Neacoryphus bicrucis (Lygaeidae), (E,E)-2,4-hexadienyl acetateand phenethyl acetate (9:1) were identified from males, and found attractiveto both sexes of adults in the field plus a tachinid fly parasitoid ofthe bugs. In N. bicrucis, the pheromone was clearly shownto come from the tubular accessory glands of the metathoracic scent gland;this evidence, plus earlier literature reports for other species, indicatethat male lygaeids are the pheromone emitters. In another lygaeid,Oncopeltus fasciatus, 2-isobutyl-3-methoxypyrazine was identifiedin the cardiac glycoside-laden fluid sequestered from milkweed hosts andexpelled by these bugs when they are attacked. Alkyl methoxypyrazinesare warning odorants associated with poisonous insect secretions, and theirpresence in O. fasciatus indicates that the plant-derived chemicaldefense of lygaeines is more elaborate than previously appreciated.