_ larvee from the inside of the right 
Ps 
THE CATTLE GRUBS OR OX WARBLES Al 
3—It is not necessary to apply friction to the eggs to cause 
them to hatch, as the larvee have been observed in many instances 
by the writers and others to crawl from the shells when their 
‘development was completed, provided the proper temperature was 
maintained. ; 
4.—Much skin irritation in areas where eggs have been attached 
to the hairs is in evidence about four days after the eggs have 
been deposited. It has been observed repeatedly that violent stamp- 
ing, kicking, and licking of the affected parts by the host occur 
soon after the hatching of the eggs begins, and a few days later 
soreness and the formation of scabs due to the exudation and 
hardening of serum are apparent. When these scabs are removed, 
a cluster of hatched eggs is usually 
found attached to the hair in their 
midst, | (His. 21: ) | 
5.—The actual penetration of a 
number of larvee soon after hatch- 
ing has been observed by the 
writers and their associates. This 
process will be described later. 
6.—Stub (95) has been able to 
trace the route pursued by young 
tibia over the shoulder and around 
the muscles of the neck to the 
connective tissue of the esoph- 
aAgUS. 
Taking the evidence set forth cs eae 
herein and considering the obser- Fic. 21.—Scab removed from a_lesion 
$ 5 g on a cow, caused by penetration of 
vations of other investigators newly-hatched larvee HOF Hypoderma 
whose work entirely corroborates lineatum.. Note the thfee hatched eggs 
: on the hair 
it, there seems now to be no doubt : 
that the normal method of ingress for the larve of both H. lineatum 
and H. bovis is directly through the skin at the point where the eggs 
are attached, and proves that there is comparatively little likelihood 
of infestation occurring by means of larvee taken in by the mouth. 
It is desirable to stress at this point the demonstration given, by the 
slaughtering of some of the animals as above outlined, that the larve 
_ entering cattle through the skin on the lower legs may be found in 
_ the gullet in considerable numbers during the succeeding months. 
This proves the fallacy of the suggestion frequently made by investi- 
gators that those larvee which are found in the gullet were probably 
taken in by the mouth and that they may perish and never reach the 
back. It should be noted that the writers have shown herein that 
larvee of H. lineatum removed in the second instar from the gullets 
of cattle and introduced under the skin of uninfested bovines will not 
only appear under the skin on the backs of the new hosts in the 
proper season, but may and probably usually do pass again into the 
body cavity and even return to the gullet before going to the back. 
DEVELOPMENT AND HABITS 
NUMBER OF EGGS ON HAIR 
The eggs of 1. lineatwm are usually laid in a series of from 5 to 12 
and occasionally as many as 20 may be attached to a single hair. The 
