126 



experiments were conducted in a crude way, without the use of special 

 bacteriological apparatus, and are, of course, open to question. They 

 tend to show, however, the bacterial nature of the disease, the presence 

 of a specific organism, and the possibility of contagion. 



Another observation serves to show the contagious nature of the 

 disease. It was noticed on August 15, 1904, that four larvse had died 

 in succession in as many nights in the same breeding jar, the dying 

 bollworms having been daily replaced by new ones. At this time a 

 thorough washing with hot water and soapsuds prevented future mor- 

 tality in the jar. We have noted many other similar instances during 

 the breeding work. 



Quite often the larva has already entered the soil before it is appar- 

 ently attacked, and, again, not infrequently a larva may die while in 

 the act of constructing its burrow. 



It is very noticeable that larvse which have been injured or bitten 

 by their fellows are much more susceptible than healthy specimens; 

 in fact, a larva which has been but very slightly hurt scarcely ever 

 escapes infection. 



At present there seems to be no hope of making any practical use 

 of the disease in controlling the bollworm, as has been done with some 

 other species of injurious insects. It is an important factor, however, 

 and helps to keep the pest in check.- 



SCAVENGERS FOLLOWING THE BOLLWORM. * 



In addition to the true parasites of the bollworm there are a num- 

 ber of insects acting as scavengers, some of which are often mistaken 

 for parasites. 



On numerous occasions we have observed minute flies, belonging to 

 the family Phoridge, hovering about the breeding jars which contained 

 specimens of larvae, pupae, and adults; in fact, it is almost impossible 

 to keep large numbers of bollworms or pupae together without attract- 

 ing these little scavengers. In one case the Phoridae were allowed to 

 oviposit upon a dead and decaying moth, and after a period of seven- 

 teen days the adults of a second generation appeared. They proved to 

 be Aphioclideta fimgicola Coq. In other lots of larvae from various 

 localities many specimens of Phora incisuralis Loew were obtained 

 at different times during the summer, and doubtless other species 

 might have been found if special search had been made for them. ' 

 Aphiochaeta nigriceps Loew {Phora aletide Comst.) has been observed'* 

 to feed upon the dead pupae and adults in the same wa}^, and was at 

 first thought by Comstock* to be a true parasite. This has been 

 abundantly disproved, ,however, and none of the species have any 

 especial economic significance, since they never attack living boll- 

 worms in an}' stage. 



« Riley, Fourth Kept. U. S. Ent. Com., p. 117. &Rept. Cotton Ins., p. 208. 



