Intersexual Transfer of a Toxic Terpenoid during Copulation and Its Paternal Allocation to Developmental Stages: Quantification of Cantharidin in Cantharidin-Producing Oedemerids (Coleoptera: Oedemeridae) and Canthariphilous Pyrochroids (Coleoptera: Pyrochroidae)

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Abstract
In whole body extracts of the canthariphilous pyrochroid Schizotus pectinicornis and the cantharidin-producing oedemerid Oedemera femorata cantharidin contents were determined by means of quantitative gas chromatography. Adults and all developmental stages of both species contain this terpenoid, but in considerably different amounts. Cantharidin contents differ significantly between the sexes of adult O. femorata: 8.4 μ,g/female, 3.5 μg/male. Values for Sch. pectinicornis are more than 30-fold lower than those of O. femorata and no intersexual difference in the cantharidin content could be detected. Eggs of O. femorata contained cantharidin and larvae of this species are capable of synthesizing this terpenoid. The total amount of cantharidin increases in successive instars. In Sch. pectinicornis, the content of cantharidin decreases from egg to first instar. Feeding and copulation experiments with [2H2]cantharidin indicate that in O. femorata no or only very small amounts of cantharidin are transferred from males to females at copulation. Thus, males do not invest in the protection of their offspring by cantharidin gifts to the mate. For Sch. pectinicornis an intersexual transfer of labelled cantharidin during copulation was detected. About 45% of the entire cantharidin content in mated females derived from fed males. Analyses of eggs and first instar larvae show that a paternal allocation of 2[H2]cantharidin to developmental stages exists for this canthariphilous pyrochroid.

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