ig22. Carpenter. — The Life-History of Warble-Flies. 77 



FURTHER OBSERVATIONS ON THE LIFE-HISTORY 



OF WARBLE-FLIES. 



BY PROF. GEORGE H. CARPENTER, D.SC. 



Eight years ago an article appeared in the Irish Naturalist^ 

 in which a summary was given of observations made by 

 the late Thomas R. Hewitt and the WTiter on the behaviour 

 of the nev/ly-hatched larvae of Hypoderma hovis and H. 

 lineatum, these observations confirming the conclusions 

 arrived at from experiments with muzzled calves that the 

 young maggots bore directly in through the skin close to 

 where the eggs are laid on the hairs, and make their way 

 thence through the tissues to the wall of the gullet, and 

 later to the well-known stations beneath the skin of the 

 back where they ripen during the spring months. 



Further details of these observations were shortly after- 

 w^ards published.^ Since then the work has been continued, 

 and a summary of the results of biological interest from 

 the latest report^ on the subject may be acceptable, as 

 these offer strong confirmation of the conclusions previously 

 set forth. 



Muzzling experiments were continued at Ballyhaise 

 during the summer of 1914 on nine muzzled and seven 

 " control " calves. The former had 261 warble-maggots 

 in the spring of 1915 — an average of 29 per beast ; the 

 latter had 62 warble-maggots — an average of less than 9. 

 It seems therefore not merely that muzzling affords no 

 protection, the maggots never finding effective entrance 

 into the host-animal by way of the mouth, but that cattle 

 free to lick their skins may destroy or dislodge many eggs 

 that have been attached to their hairs. 



But it was desired to supplement these muzzling 

 experiments and the direct observations made of the 3'oung 

 maggots' entrance through the skin, by experiments in 



•^ vol. xxiii., 1914, pp. 214-221. 



^ Journ. Dept. Agric. and Tech. Instr., Irel., vol. xv., 1914, pp. 105-132. 



^ lb., vol. xxii., 1922, pp. 14-25. 



