STRUCTURE AND FUNCTION OF THE TERMINAL ABDOMINAL APPENDAGES (PYGYPODIA) OF PHOTURID FIREFLY LARVAE

¹ Department of Biological Sciences, State University of New York at Albany, Albany, New York 12222

The morphology of the pygypodia, the eversable terminal appendages of the abdomens of photurid firefly larvae, was studied with particular reference to the integumental and muscle systems. The eversable nature and observed versatility of these appendages apparently result from the antagonistic action of pygypodia-associated muscles and those muscles which control (pseudo)coelomic fluid pressure in the abdomen, as well as from several fine structural features of the integument. Continuous sheets of parallel microfibrils in the endocuticle form a tough elastic inner sheath within each pygypodium. The integument bears rows of spurs, whose interconnection by the microfibril sheets may aid in their positioning as well as in their orderly and consistent packing during inversion and eversion of the pygypodia. The loose organization, irregularity of shape, and sparsity of sites of attachment of the epidermal cells, relative to the basement membrane, may all contribute to the flexible, yet strong, inner structure of the integument.