CHEMICAL DEFENSE IN CHRYSOCHUS LEAF BEETLES

Susanne DOBLER-a, Jacques M. PASTEELS-b, Desire DALOZE-b
a-Universität Freiburg, Biologie I, Albertstr. 21 a, 79102 Freiburg, Germany;
b-Université Libre de Bruxelles, Laboratoire de Biologie Animale et Cellulaire, 50 Av. F. D. Roosevelt, 1050 Bruxelles, Belgium

Chemical defense by secretions released from glands on the pronotum and elytra has been well described for several related subfamilies of leaf beetles (Chrysomelinae, Alticinae and Galerucinae)-1. Here we report a similar phenomenon from an unrelated subfamily of leaf beetles, the Eumolpinae,-where defensive secretions have not been described previously and might constitute a parallel evolution. In the European Chrysochus asclepiadeus secretions are abundant and protect the beetles against ant predators. So far, aromatic amino acids and diacetyl- putrescine have been identified in these secretions. Two North American species, C. cobaltinus and C. auratus, feed on cardenolide containing plants of the genera Asclepias and Apocynum and trace amounts of cardenolides can be detected in the beetles. The secretions of these species are of much smaller volume than those of their European relative, nevertheless the insects are protected against invertebrate predators. We hypothesize a synergism between food plant toxicity and the amount of secretions produced.