Januar)-— Febuary iSSS. 



PS2'CHE. 



sects are readily divisible into two 

 principal groups ; schizomycoses, pro- 

 duced by bacteria, and h}'phomycoses, 

 due to fungi which form a more or less 

 evident mycelium of cylindrical threads 

 (^Hyphomycetes and Pyrenoinycetes) . 

 These are roughly distinguishable in two 

 important particulars : (i) The bacteria 

 invade the body from within, by way 

 of the alimentary canal ; and the thread 

 fungi penetrate from without through 

 the skin or spiracles ; (2) Death from 

 a schizomycosis is followed by rapid 

 decay, which soon reduces the tissues 

 to a putrid fluid ; while after death 

 from a hyphomycosis the often flaccid 

 body hardens and mummifies without 

 decay, usually swelling to more than 

 its usual size, and frequently becoming 

 covered with a flour-like efflorescence 

 of spores or spore-like bodies. These 

 last characters distinguish the hypho- 

 mycoses from the pebrines, — the body 

 mummifying in the latter, but shrivel- 

 ing at the same time and never covering 

 itself witli spores, unless with those of a 

 common mould of post ?)iorfe?n devel- 

 opment. Further, ihe pebt'if/e mummy 

 contains only the minute oval spores of 

 the parasite, while that of a hyphomy- 

 cosis contains either a mass of mycelial 

 threads or large thick-walled, spherical 

 spores, — the lasting spores of an Etito- 

 mophthora or, possibly, both spores 

 and mycelium together. 



Muscardine, longest-known of insect 

 diseases — often a cause of astounding 

 destruction both to domesticated and 

 native species, and by far the most 

 promising natural agent for the artificial 

 restriction of noxious insects — is caused 



by a niunber of fungous forms — Botry- 

 tls, Isaria^ Cordyceps^ — several species 

 of each — the classification and ontogenet- 

 ic relations of which are not yet wholly 

 settled. Some Botryiis forms have 

 been unmistakably connected with 

 some Isarias as an earlier developmen- 

 tal stage, and other Botrytis forms 

 have been as clearly connected with 

 Cordyccps^ while all the entomochthon- 

 ous Isarias are classed by Cooke as Cor- 

 dyceps in a vegetative stage ; but, on 

 the other hand, the longest-knov^'n 

 Botrytis — that of silkworm muscardine 

 — has never been followed, that I can 

 find, beyond an Isa7'ia stage, and other 

 species are in doubt. Hence, as one 

 consciously beyond the limits of his prop- 

 er territory, I will touch these dubious 

 and contested matters in the lightest 

 way, endeavoring onl}- to get at and 

 apply the very important entomological 

 data which the cryptogamic botanists 

 have incidentally worked up for us. 



Generalizing the life histories of 

 these fungi and their modes of attack 

 on the living insect structure (which 

 is for most of them the indispensable 

 substratum of their later growth), we 

 may say that they invade their hosts 

 from without — or, sometimes, by the 

 spiracles and tracheae — but never, so 

 far as known, by way of the alimentary { 

 canal ; that their minute spores germi- 

 nate on the surface and send inward 

 through the cuticle slender threads which 

 grow through the body wall and then 

 separate into small single cells — cylin- 

 drical conidia — that these pass every- 

 where, growing, dividing and again 

 dividing as they go, deriving their nutri- 



