The hish Nahiralist, 
October, 
SOME NEW OBSERVATIONS ON THE LIFE-HISTORY 
OF WARBLE-FLIES. 
The Entrance of the Maggot into the Host's Body. 
by prof. george h. carpenter, m.sc, and 
thomas r. hewitt, a. r. csc. i. 
The life -history of the Ox Warble -flies (Hypoderma bovis 
and H. lineatum) has been for many years a subject for 
enquiry by naturalists and veterinary surgeons as well as 
by fanners. Those interested in the progress of research 
into the question will find the main results obtained up to 
the end of last century well set forth in an article by Imms.^ 
It was then established that the eggs are laid attached 
to the hairs of the cattle, that the second-stage maggots 
may be found abundantly in the sub-mucous coat of the 
gullets of oxen and heifers from August onwards, and 
subsequently wandering through various tissues in the 
dorsal and lumbar regions, and that in this second stage 
they arrive beneath the skin of the back, where in late 
winter and spring the third-and fourth-stage larvae are 
familiar objects, inhabiting the swellings or " warbles," 
each pierced by a central breathing -hole through which 
the "ripe" maggot works its way for pupation on the 
ground. So far, however, the first -stage maggot was known 
only from Riley's figure^ of an unhatched specimen, and no 
certain knowledge had been obtained as to its mode of entry 
into the host animal's body. Formerly it was generally 
believed that the femiale fly lays her eggs on the back, and 
that the maggots bore their way in directly through the 
skin. But the observations of Curtice and Riley that in 
North America the female H. lineatum lays her eggs mostly 
on the heels and that second-stage maggots appear com- 
monly in the gullet, have led in recent years to a general 
behef (at least among entomologists) that the eggs— or, as 
1 Journ. Econ. Biol., vol. i., 1906, pp. 74-9* 
2 Insect Life, vol. iv.^ 1892, pp. 302-17. 
