174 



riutn, a figure of which showing the lid detached, we reproduce from 

 Clark's earliest paper (see Fig. 34). 



The facts in the life-history above given are for the most part well 

 understood, and there has been little difference of opinion among au- 

 thorities except as relating to the exact manner of the deposition of 

 the egg. Those who believe that the eggs are thrust into or beneath the 

 skin express a belief admittedly not based upon observation, and con- 

 trary to all analogy. That there should be differences of opinion upon 

 a question where observation is so difficult is, perhaps, not to be won- 

 dered at. It is extremely difficult to follow the movements of the 

 parent fly on an animal rendered restless or frantic by her presence or 

 her attacks, and it is further quite difficult to discover a single egg con- 

 cealed by the hair of the animal's back. The manner of placing the egg 

 given by us in the article quoted above is based on experience with war- 

 bled cattle in Illinois from 1860-'63, when we were interested directly in 

 stock raising, had charge of some three hundred head of cattle, and had 

 frequent opportunity to examine and study the grubs in situ and the 

 habits of the perfect insect. 



Fig. 33. — ftypoderma bovin: a, egg; b, full-grown larva, ventral view; c, puparium, ventral view; d, 

 newly hatched larva, side view; e, anal stigmata of larva, — all enlarged (after Brauer). 



It is a long time ago and we made no definite notes at the time, but we 



believe that we can trust our recollection. Analogy, unity of habit in the 



family, and structure all confirm it and are against the belief in insertion. 



A careful study of the structure of the egg (Fig. 33 a), which we have 



seen in this and in a very closely allied species, 



ujj^ figs JM B . tne so-ca ^ e( l Heel -fly (Hypoderma lineata), as 



J§ llfgp Jp wL well as the descriptions and figures by other 



m ■ ^ W5-\ M authors, show that the grooved and slightly 



1| '0 wlw pediceled enlargement of the end which is 



vV'- y ' ^jp attached is admirably adapted for being 



strongly fastened to the skin and to the base 



of the hairs, and all observations that have 



been recorded point to the fact that the young 



larva works its way directly from the egg under 



the skin, as is the case with other parasitic 



Fig. 34.— Hypoderma bovis : a, 

 puparium, from side; b, same, 

 from below, showing exit hole 

 of adult; c, cap which splits off 

 to allow the adult to issue — nat- 

 ural size (after Clark). 



