Current Topics in Insect Endocrinology and Nutrition

Stanley Friedman University of Illinois Urbana, Illinois A perusal of the table of contents of this short symposium on Insect Endocrinology might lead those who are generally unin- structed in Fraenkel's activities to wonder as to our choice of papers. Our justification is based upon our effort to concentrate the symposium upon a single area in which he has had an extended involvement: namely, the metamorphic molt in flies. In so doing, we immediately recognized the enormous humoral and physiological ramifications, both direct and indirect, of such an interest. Our selection of these papers is an attempt to present the broad picture with a few quick strokes. The first offering, by J. H. Willis, et al., is a direct outgrowth of Fraenkel's work with Rudall on the chemistry of the puparium. Their investigations on the structure of fly cuticle and its changes at pupariation (Fraenkel and Rudall, 1940, Proc. Roy. Soc.London (~) 129:1; 1947, ibid, 134:111), provided quanti- tative data which have,since that time, influenced our ideas con- cerning cuticular changes at metamorphosis and are presently at the center of the controversy over the mechanism of cuticular hardening and darkening (see Hillerton and Vincent, 1979, l. Ins. Physiol.