ANIMAL PARASITES AND DISEASES. 65 



active, though in some cases they were inactive and apparently dead. 

 About five weeks after collecting the eggs nearly all gave only inactive 

 or dead larvae, though opened with ease on being touched by the 

 finger, and in forty days after collecting no living larvae could be 

 found in the remaining eggs, except one which had succeeded in push- 

 ing off the cap of the egg and partially emerging. 

 In view of these results, I concluded : 



(1) That the eggs of the horse bot fly do not hatch, except by the 

 assistance of the horse's tongue. 



(2) That hatching does not ordinarily occur within ten or twelve 

 days and possibly longer, or if during this period, only on a very 

 continuous and active licking by the horse. 



(3) That the hatching of the larvae takes place most readily 

 during the third to fifth week after deposition. 



(4) That the majority of the larvae lose their vitality after thirty- 

 five to forty days. 



(5) That the larvae may retain their vitality and show great 

 activity upon hatching as late as thirty-nine days after the eggs were 

 deposited. 



(6) That it is possible, though not normal, for eggs to hatch 

 without moisture or friction. 



(7) That in view of these results, the scraping off of the eggs, or 

 their removal or destruction by means of washes will be effective, even 

 if not used oftener than once in two weeks during the period of egg 

 deposition, and, probably, that a single removal of the eggs after the 

 period of egg deposition has passed, will prevent the great majority of 

 bots from gaining access to the stomach, or at least so large a propor- 

 tion that little injury is likely to occur. 



Wishing to know still more definitely the period of most ready 

 hatching, and the effect of different washes for treatment, I suggested 

 to a veterinary student, Mr. Harry Shanks, a careful series of observa- 

 tions, which were carried through during the summer of 1894. 



From this study, which was made under my direction, and so that 

 I had frequent opportunity to note progress, a number of points were 

 gained, which are worth adding to the above record. Three hundred 

 eggs were collected from a horse which had been previously freed from 

 eggs, so that the exact date of deposition was assured. The eggs 

 were tested every day. 



