66 Parasites of Cattle and Sheep. 
been taken for granted that the fly which deposits the eggs on 
the skin or hairs is the ox warble or bot fly ( Hypoderma 
bovis ), (Fig. 1), and that the eggs gain access to the depths 
of the skin at the spot in which they are inserted or deposited. 
The softness and non-resisting character of the egg-depositing 
tube has always proved more or less an obstacle to the 
acceptance of that view of the entrance of the parasite into the 
skin. Recently the view has been advanced that another fly, 
the Hypoderma lineata , or American Heel Fly, deposits its 
eggs on the hairs, particularly of the legs of cattle ; that these 
eggs, or larvae developed from them, are licked off by the 
animal, pass into the gullet, which they pierce, and in this 
indirect way reach the skin. Fortunately, neither of these 
questions need affect the stock owner, whose object is to avoid 
their occurrence in his cattle. The maggots appear from 
January to May in the skin, and here they are found with the 
tail end, in which is the breathing pore, at the perforation 
at the summit of the warble. The number of warbles in the 
skin, f individual animals varies widely ; in some, only a 
sin$ r 3 specimen may be found, while hundreds may reside in 
a superficial foot of hide. A few warbles 
cause little inconvenience to their host, but 
when very numerous, great discomfort, local 
injury, and loss of flesh may ensue, and 
under any circumstances, the unbidden 
guest cannot be welcome. It is, however, 
fig. i— The Ox Warble to the hide that the greatest damage is done ; 
Fly ( Hypoderma bovis). & -£ ew war kl es ma y spoil a large portion, 
while many will render it practically useless . 1 The losses on 
account of warbled hides are stated to amount in the aggregate 
to several millions of pounds annually ; while, when the warbles 
are numerous, considerable portions of beef may be unfit for 
sale. Underneath the skin containing warbles there is found 
a somewhat jelly-like substance, which has a very dirty 
nauseating appearance. Flesh so affected is termed “ licked 
beef.” When considering the effects of this fly, we must take 
into account the unrest, sometimes amounting to “panic,” the 
consequent loss of flesh and milk, and other possible injury 
to the in-calf cow, attributed to the apparent terror of animals 
while the eggs are being deposited. During this act, the warble 
fly is credited with producing a buzzing sound, hovering over 
the animal, making a sudden dart on to the skin, leaving an 
egg, and repeating the operation many times. As there is still 
wanting proof that the warble fly possesses any weapon with 
which the skin may be hurt, we think it probable that any 
1 See also page 207 of this Volume. 
