Distribution of adult defense glands in chrysomelids (Coleoptera: Chrysomelidae) and its significance in the evolution of defense mechanisms within the family.

Defense glands were examined in the adults of 65 species belonging to 10 different subfamilies. They were found in the pronota and elytra of members of the subfamilies Criocerinae, Chrysomelinae, Galerucinae, and Alticinae. It is suggested that these glands appeared monophyletically in the course of evolution and that the absence of glands in several species of the two most evolved subfamilies is a secondary event, explained by the presence of alternative efficient defensive behaviors: reflex bleeding in the Galerucinae and escape mechanism of jumping in the flea beetles. It is also suggested that a large distribution of the glands at the surface of the beetles is a primitive condition and that in the course of evolution only the glands most efficiently located along the edges of the pronotum and elytra were maintained. Such evolution has occurred several times. Alternative and complementary defensive mechanisms are also listed and discussed.