DIPTERA. 93 
mouth and alimentary canal, as will be discussed more fully under /in- 
eata. While from analogy it seems very probable that a similar habit 
will be proven for bovis I know no positive obser- 
vations, but Miss Ormerod adheres to the belief 
that the entrance for that species is through the 
skin. 
In either ease the maggots, as a rule, must be 
within the animal as early as October (for lineata 
much earlier), and by January the lumps or swell- 
ings along the back denoting their presence be- 
come appreeiable, and growth continues as late 
as April and possibly May, varying with latitude. 
We have quite fully developed specimens (of 
lineata) taken March 25, from the backs of cattle 
at Ames, lowa, at which time they were mostly 
well grown and some of them apparently about 
Fig. 38.—Hypoderma lineata: 
ready to escape from the ulcer. After working  ovipositorof female: a, from 
their way through the opening in the hide,in “4°” 8P: ftom below— 
enlarged (from Insect Life). 
which they are assisted by the prickly tubercles 
covering the body, they drop to the ground. The full process is thus 
described by Dr. Williston (Stand. Nat. Hist., pp. 427-428): 
They have the peculiar ability to contract either end into an elongate cylindrical 
form, which not only serves them in their egress, but also to bore into the ground. 
A few days before they are ready to emerge they begin to enlarge the opening by 
this expansion and contraction; when they have enlarged it sufficiently, a ring-like 
contraction of the body that begins at the posterior part and progresses toward the 
head enables them in a few minutes to free themselves, which they usually do in the 
morning hours. Upon the ground they creep about until they meet some obstruc- 
tion, when they burrow from 1 to 2 inches below the surface, and remain as in the 
Gastrophiius species. 
They remain in the ground as pupe for about a month and then issue 
as flies. 
REMEDIAL MEASURES. 
Knowing that the insect occurs, during nearly three months of the 
year at least, in no other place than in the backs of cattle, it is evident 
that the destruction of all the grubs in the back of every animal 
between January and April must result in the extermination of the 
pest. That there are measures sufficient to accomplish this destruction 
is certain, and at an outlay of time and trouble that makes them prac- 
ticable with every man who owns cattle, whether one or ten thousand. 
Indeed the insect is open to attack in at least three different ways: 
(1) Measures to prevent the deposition of eggs; (2) measures to destroy 
the eggs or young grubs; (3) measures to destroy the grubs after 
passing under the hide. : 
To prevent the deposition of eggs the application of some persistent 
sticky substance may be recommended, or this may be combined with 
some substance of obuoxious smell, 
