Jean-Luc BOEVÉ, Monika MILKER
Institut for Zoologie, Freie Universität Berlin,
Haderslebenerstr. 9, D-12163 Berlin, Germany
Sawfly larvae of the tribe Phymatocerini are specialists on one plant taxa such as Veratrum, Polygonatum, /ris, Helleborus, Ranunculus or Poaceae. A sequestration of alkaloids from Veratrum is known to occur in one sawfly species [1]. The question is whether sequestration is a general phenomenon for the Phymatocerini. It would bring us to a rare situation where closely related insect species have to deal chemically with a large variety of secondary plant metabolites which possess toxic properties. In the plant genera mentioned above, steroidal alkaloids, quaternary alkaloids, steroid saponins, spiro-bicyclic triterpenoids, and lactones are major chemical types. Most of these chemicals are known to have a toxic effect on vertebrates and/or invertebrates. During a field season in Switzerland. eight Phymatocerini species were collected. The integument of the larvae was wounded easily, and disturbed larvae remained immobile. Moreover, the hemolymph of the larvae, tested on ants, proved to act as a feeding deterrent. By chemical analyses, the hypothesis that sequestration could occur recurrently in several species was investigated. I discuss from an evolutionary point of view the question whether sequestration could have evolved as a trait related to the high toxicity of secondary plant metabolites.
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