BIOSYSTEMATISTS Meeting, Feb 12th, 2004, at UCB

Caroline S. Chaboo - Program in Arthropod Systematics, Cornell University and American Museum of Natural History

Untangling fecal shield architecture in tortoise beetles: behavior, ecology, morphology and phylogeny (Coleoptera: Chrysomelidae: Cassidinae)

ABSTRACT: Animal constructions are a fascinating subject in natural history. Understanding diverse constructions such as bird nests, ant hills, wasp nests, caddis fly cases, termitariums and spider webs requires information about the behavioral end-products (materials and architecture), construction behavior, life history, ecology, morphology, and phylogeny.

The beetle family Chrysomelidae (leaf beetles; ~40000 species) is not well-known as a building group, however species in several subfamilies recycle their feces into constructions. In tortoise beetles (Subfamily Cassidinae; ~6000 species) the larval stages, and sometimes pupae, mold their feces and exuviae into an elaborate shield which is carried like an umbrella over the body. When larvae are under attack, this odd structure is flexed towards intruders or held flat on the dorsum. Several hypotheses have been developed to explain functions of shields and some of these have been tested in small comparative studies of 1-3 species. The intrinsic influences of morphology and phylogeny have been omitted entirely from this discussion, thus limiting a broader understanding of the origins and radiation of shield architecture.

The first goal towards untangling this complicated story was to construct a phylogenetic hypothesis for Cassidinae (my doctoral research at Cornell). In this paper I develop a descriptive terminology for shield architecture, discuss the specialized morphological structures associated with shield construction, and present a first-generation hypothesis to explain the origin and radiation of these functionally-correlated features.