376 WEST VIRGINIA EXPERIMENT STATION 



dark semi-liquid mass which gave off a repulsive odor when the 

 body wall was broken. 1 



Many examples of both larvae and pupae were found in May 

 which had apparently died quite recently ; since they had, at 

 that time, the normal whitish color. The body was greatly ex- 

 tended as if inflated with air, and upon breaking the skin, the 

 internal structure was found to be decomposed. Therefore, while 

 the severe cold of December, 1892, and January, 1893, and sub- 

 sequent changes in temperature weakened the vitality of the 

 insect, and must have killed many of them outright, the exter- 

 mination of the species over such a vast area,was doubtless made 

 doubly sure by the action of one or more contageous diseases 

 which found the conditions especially favorable for its spread 

 in the weakened vitality of the larvae and pupae that survived 

 the winter. 



That a disease alone could accomplish this end appears all 

 the more probable, when we consider how epidemics among 

 other kinds of insects known to be due to diseases almost exter- 

 minate the species over vast areas. 



The chinch bug is attacked by a disease, which, under favor- 

 able climatic conditions, as continued wet weather, is practic- 

 ally exterminated over extensive areas within a few days. In 

 fact, the disease may be successfully transmitted by artificial 

 means from a locality or region where it is prevalent, to one in 

 which it has not manifested itself; and thus produce an epi- 

 demic that spreads with remarkable rapidity. The disease of 

 the clover leaf beetle is perhaps the most remarkable example 

 of the effects of the disease upon insects. The clover leaf 

 beetle (Phytonomus punctatus, Fab.,) is a native of Europe ; 

 but has become widely distributed over the northern and east- 

 ern United States. It is capable of enormous increase from a 

 comparatively few surviving individuals; and we often find in 

 the early spring, that the total destruction of the clover crop 

 over vast area of country, is threatened by myriads of small 



F 1. The same condition has since been observed with examples of larvae of Scolytus 

 rugulosus, Pityophthorus minutissimus and. Chrqmesus icoriae which were known to be, 

 killed by freezing. 



