THE NATURE OF THE POLYHEDRAL BODIES FOUND IN INSECTS. 1 R. W. GLASER AND J. W. CHAPMAN. CONTENTS. 1 . Introduction 367 2. The polyhedral bodies 369 3. Origin of the polyhedral bodies '. 373 4. Bio-chemical observations 376 5. Summary 382 6. Bibliography 383 7. Explanation of Plates 386, 388 INTRODUCTION. A very large group of lepidopterous larvae is subject to a class of infectious diseases known as the "polyhedral diseases." Whether the organism concerned in their production is identical or not for all the species of insects affected must remain a matter of conjecture till further work allows us to venture an interpreta-tion. One thing, however, is certain, namely that curious crystal-like structures called "polyhedral bodies" or "polyhedra" are always associated with the type of diseases we are here dis-cussing. Although these polyhedra may vary considerably in size and somewhat in shape in the different species of insects, nevertheless, they are always specific for a certain type of malady. Wahl, followed by Prowazek and Escherich, consider the polyhedral diseases as distinct and absolutely divorce them from the fungous, protozoan and bacterial affections of insects. We believe that the erection of a separate group to embrace all of the polyhedral diseases is an excellent plan and receives our sympathetic endorsement, for the reason that the confusion of all of the insect diseases is still common amongst entomologists. We venture to say that there are scarcely two entomologists in America who know the difference or similarity between any of the diseases expressed by such terms as Muscardine, Pebrine, 1 Contribution from the entomological laboratory of the Bussey Institution in cooperation with the U. S. Bureau of Entomology (Bussey Institution No. 115). 367
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