1Institut für Biologie I (Zoologie), Universität Freiburg, Hauptstr. 1, D-79104 Freiburg, Germany.
2Zoologisches Institut (Abt. Ethologie), Universität Bonn, Kirschallee 1, D-53115 Bonn, Germany.
Pairs of the tenebrionid beetle P. armaticeps (Stizopina, Opatrini, Tenebrionidae) raise their brood in burrows in the sands of the Kalahari desert. Individuals of a closely related species, E. opacus, lay their eggs as cuckoos in the host's burrows. Adult kleptoparasites are attracted to their hosts by a volatile kairomone. A potential source is the pygidial gland. Major constituents are 1,4-benzoquinone, 2-methyl- 1,4-benzoquinone, 2-ethyl- 1,4-benzoquinone and 1-alkenes (C11, C13, C15). A series of hydrocarbon monoterpenes were identified as additional compounds, such as (-)-alpha-pinene, (-)-camphene, (-)-beta-pinene and (-)-limonene. In a laboratory bioassay, two alternative hiding places with silicon rubber septa, one of which was spiced, were offered to individual E. opacus. Beetles showed a significant attraction to the defensive secretion milked from P. armaticeps. We formulated mixtures of the three classes (benzoquinones, 1-alkenes and terpenes, respectively) from synthetic compounds at natural concentrations. Only the terpene mixture attracted E. opacus, and of the individual terpene components, only (-)-camphene.