634 MICROBIAL DISEASES OF INSECTS 



Entomogenous Fungi.* — The practical usefulness of some of these 

 species, notably Sporotrickum globuUjerum, as a chinch-bug disease, has 

 been studied carefully. While the work was markedly successful in 

 causing an epidemic disease when conditions favored it, dependence 

 upon particular conditions was so complete that the production of the 

 disease as an efEective destroyer of pests failed. Similar results have 

 attended the effort to use other fungi as insect-destroyers. The condi- 

 tions which make possible their development in epidemic form only 

 occur occasionally. These conditions in themselves are, as a rule, 

 very unfavorable to insects. Under other cUmatic conditions, these 

 diseases appear only as isolated cases, negligible in their effect upon 

 the insect population, no matter how carefully the inoculating 

 material is spread by man. 



Bacterial Disease or June Beetle "Lasvm, Lachnosterna spp. 

 Micrococcus nigrofaciens — Northrupf ' 



History and Distribution. — The characteristics of this disease 

 were noted in 1893 by Krassilstschik, Russia, but he did not consider 

 it a disease. It is common everywhere in the United , States that 

 white grubs of this and related species are found; infected specimens 

 have also been received from Porto Ricb. 



SvMPToks. — The normal larva is white, quite firm, covered with 

 conspicuous hairs; the head is brown as are also the spiracles or breath- 

 ing pores along either side. The diseased larva has black shiny spots, 

 sharply circumscribed, located mainly along the joints of the legs, 

 spiracles, and upon the dorsal or ventral segments of the white portion. ' 



Badly diseased larvae are almost entirely black or brownish black 

 in color; the whole body often seems to be in a state of advanced putre- 

 faction, yet the larva still shows life. 



The progressive destructiveness of the disease is most marked in 

 the affections of the legs. In some cases the infection begins at the tip 

 of the leg and as it progresses, the leg, segment by segment, blackens 

 and drops off, leaving the stumps shiiiy, black, and sometimes swollen 

 ill appearance; in other cases the infection occurs at one of the inter- 

 mediate joints or at the joint nearest the body of the grub, the leg in 



* Prepared by Charles Thom. 



t Northrup, Z. A bacterial disease of June beetle larvas, Lachnosterna spp. Tech. Bwl. 

 18. Mich, Exp. Sta., 1914. 



