GASTROPHILUS HAEMORRHOIDALIS AND OTHER BOTS. 29 



Upon the suckling colt the first egg disappeared upon the ninth 

 day ; the eleventh day, two ; the thirteenth, five ; and the fourteenth, 

 six. Five other eggs about 1 inch from the mucous membrane and 

 upon the dry portions yielded dead larva? when examined. 



Upon the lips of the cripple horse and within 1 inch of the mucous 

 membrane 15 eggs were deposited. The first 6 eggs disappeared 

 upon the seventh day from near the corners of the mouth. The last 

 egg disappeared upon the eighteenth day. 



The normal horse in grazing received 14 eggs within 1 inch from 

 the mucous membrane. Upon the sixth day 10 eggs disappeared 

 from near the corners of the mouth, which was probably five days 

 from deposition. The other 4 disappeared during the following 

 three days. 



The striking feature of the above three cases is that those eggs 

 deposited where they received most moisture and friction were the 

 first to disappear. Prior to disappearance, the color changes, being 

 first brownish, then a brownish red, finally with a whitish tip, thus 

 clearly indicating embryonic development. It is also clearly seen 

 that the amount of grazing affects the incubation, as the normal 

 horse grazed practically the whole time, the cripple only at times, 

 while the suckling colt was not observed to graze. There were no 

 indications that the larvae burrowed into the lips, and as well-incu- 

 bated eggs have produced larvae under moisture and friction when 

 removed, it is certain that the method of ingress of larvae into the 

 host is not unlike that of G. intestinaUs. It is true that eggshells 

 were never found attached to the hairs after the larvae had emerged, 

 but it is believed the moisture and friction are sufficient to remove 

 these after the larvae leave the eggs and enter with the food. 



Incubation records are not confined to the above three cases. 

 Upon August 24, 1915, one other animal was freed of eggs and 

 allowed to receive depositions during 24 hours. Upon the moist 

 portions of the lips 17 eggs were found, while 6 were deposited 

 upon the dry portions 1 inch from the mucous membranes. Separate 

 notes give a comparative idea of the incubation. Upon the sixth 

 day, probably 5 days from deposition, 4 eggs disappeared from the 

 moist portions and others disappeared the following day. Upon 

 the dry portions all were present upon the twelfth day. Three of 

 these when removed contained dead forms and the other 3 disap- 

 peared from the eighteenth to the twenty-third day. 



The day of oviposition in the above cases was favorably followed 

 by three cloudy days, which prevented other ovipositions. The de- 

 velopment of the embryo in eggs upon moist portions was quite in 

 contrast to those upon the dry portions, showing clearly the necessity 

 of moisture and friction. Such observations indicated that those 



