308 



The eggs, so far as the observations of my correspondent go, have 

 failed to liatch when removed from the animal and placed in moist sit- 

 uations, but an examination of some received, which were placed in 

 alcohol as soon as collected, shows that the larvte in them were already 

 fiilly developed. In fact, there is every reason to believe that, as in 

 the case of so many other Diptera, the embryon is already fully devel- 

 oped when the egg is laid — which confirms the view that the larva is 

 licked up by the tongue of the animal either directly out of the egg, as 

 in the case of that of Gastrophilm equi, the Horse Bot, or, as must more 

 often happen, is taken with the egg still attached to the hair, as the 

 egg-laying season is coincident with the shedding season, and cattle 

 have a great habit of licking themselves at this particular time, thus 

 taking a great deal of hair not only into the mouth, but, as we know, fre- 

 quently into the stomach as well, where it forms the well-known hair- 

 balls. In either event the larva? would seem to need the heat and 

 moisture of the animal's saliva for their well being. That the larva is 

 easily released from the eggshell is shown by the fact that the shell 

 splits open very readily at its anterior end. 



When we come to look more closely into the matter, the old idea that 

 the larvjB enter directly from the egg into the animal through the skin, 

 seems otherwise quite untenable, for the delicate larva w^hich would 

 hatch on the flanks, legs, and tail of the animal would scarcely be able 

 to wander to the back and penetrate the skin in the locations where 

 the warbles are always found, all of which lends confirmation to the 

 views here presented, viz, that the larva is licked into the mouth and 

 wanders as described, through the esophagus into the subcutaneous 

 tissue, finally reaching the dorsal region. 



The observations here recorded render significant the fact that this 

 insect is known by stockmen, particularly throughout the South and 

 West, as the Heel Fly, a name which has originated from the fly hav- 

 ing been noticed in some instances to oviposit on or near the heel of the 

 animal. Thus of ten reports received from stockmen in Texas, seven 

 say that the fly oviposits on the heel or just above the hoof, two on the 

 belly and sides, and one did not know.* 



It would thus seem that the normal place of oviposition, when the 

 animals are on their feet and moving, is somewhere near the heel, from 

 which the popular designation comes, and judging from the habits of 

 other bot-flies, in which the method of oviposition is characteristically 

 distinct, we may safely conclude that the method here described is the 



* Mr. Conr<ad L. Fuchs, Tiger Mill, Burnet County, Texas, writes, in substance, as fol- 

 lows: ''When 1 was using a half-broke ox team some fifteen years ago I could not 

 work them (on account of this fly) without keeping their heels smeared with kero- 

 sene. This I applied by means of a rag tied to a long stick. The steers soon learned 

 the benefit and would allow me to apply the oil without kicking. The fly would 

 hesitate to oviposit ('take a hold or sit to the heels'), thus giving a chance to see it. 

 Except for this hesitation it could not be seen because of its quick flight. 



