176 Cincinnati Society of Natural History. 



counted at one time the dead bodies of seventeen of these 

 caterpillars, and clustered on the top of a post, within an area 

 of twelve square inches, were six additional ones, all rigidly 

 attached to the wood, some of these bodies remaining in place 

 until the following June. 



As indicating the probable effect of this scourge, I will say 

 that at a corresponding season of the present year, 1893, there 

 is in this same locality scarcely a larva of this species to be 

 found. As the caterpillars are not gregarious, and scatter 

 soon after hatching from the ^^^, the chances of their being 

 reached by the spores of the Empiisa are • very few, unless 

 they rub against a diseased larva, or come within a certain 

 radius of such a one when the spores are thrown off, or 

 " shot," as it is termed. Hence, as now appears, this mor- 

 tality is largely due to the cause indicated, and which seems 

 to be a powerful agent in holding the species in check. 



From the fact that the victims of Empusa-^XX.'a.QV seek the 

 very highest points within their reach before they become 

 helpless, it may be suggested that they were contaminated 

 before reaching the fence, and only took to it as the highest 

 object within their reach. This appears to me to be hardly 

 possible, except to a liinited degree. The chances of infec- 

 tion elsewhere were comparatively small at most, and I have 

 observed the caterpillars, in other years, and in widely-distant 

 localities, crawling along the top board of fences in precisely 

 the same manner, with no indication whatever of the presence 

 of Empusa. So far as I have been able to observe, the victims 

 become helpless soon after contagion, though it may be that 

 much depends on the weather at the time. However, there 

 seems to be no good reason why, even under circumstances 

 most likely to delay the effects of the contagion, dead larvae 

 should not have been found on the weeds and other herbage 

 along the fences, which was but rarely the case. There 

 appears every indication that infection took place after the 

 victims reached the fence, though, of course, this is by no 

 means proven. 



It seems possible that a larva might occasionally become 

 infected by eating of a leaf that had been partly devoured by 

 another in which the disease had reached an advanced stage ; 

 or spores, in being thrown forth from a defunct larva, might 



