34:2 Illinois State Lahoratory of Natural History. 



seen that evidence of the contagious nature of the disease 

 was clear, and after August 17 the cage used in Experi- 

 ment 1 served as a general source of infection mate- 

 rial. The observations show that the greatest mortality 

 was probably from three to six days after the introduc- 

 tion of the disease, and no dead insects were in any case 

 found at the expiration of the first day. The proportion 

 of deaths was undoubtedly greatest among the younger 

 nymphs, but many adults also succumbed. Subsequent 

 experiments likewise confirmed this conclusion, although 

 the difference was not always very great. 



Characters of the disease. — The effect on the insect and 

 the post-mortem appearances were carefull}^ noted in Ex- 

 periment 1. A few hours before death the insect may 

 be found in a sluggish condition, resting low on its 

 ventral surface, and often apparently incapable of rais- 

 ing itself erect, or of crawling without a marked drag. 

 If placed on its back, it has no power to return to the 

 normal position. As the disease progresses the insect 

 loses nearly all muscular activity, and a slight waving 

 of limbs and anteunse may be the only indication of 

 life. Squash-bugs cannot attach themselves strongly 

 to the leaves by their limbs; and as they usually fre- 

 quent the under surface of the leaf, diseased bugs are 

 commonly found on the earth of the cage. 



A few hours before death there is no marked discolor- 

 ation of the body; but the insect becomes slightly darker 

 as death approaches, owing probably to changes in the 

 body fluids. After death the changes are rapid. The 

 nymphs soon assume a deep purplish black hue, the body 

 does not shrink at all, but appears tense and slightly 

 swollen, and in the course of twenty-four hours or more 

 it becomes a mere sack of gruel-like fluids. In this con- 

 dition the walls readily collapse, and the insect may not 

 bear lifting without breaking. In the adults the body 

 is observed to have a rather moist appearance at the 

 time of death, especially in the cephalic region of the 



