1922. CARPENTER. — Tkc Lifc-Histuyy of Warble-Flies. 79 



on one occasion naturally laid, the three that survived all 

 had many ripe maggots. One of these, seen to have been 

 ''struck" 187 times by a female H. bovis, had 41 maggots 

 all of that species ; another " struck " 73 times had 23 

 maggots ; another seen to have been struck 14 times had 

 13. In all cases the fly seen to lay eggs and the resulting 

 ripe maggots were of the same species. All the eggs were 

 laid below the hock on this one carefully controlled occasion ; 

 the calves were kept housed through all the rest of the 

 summer so that they had no other chance of infection, and 

 for a week after exposure to the attack of the flies they 

 were always muzzled or tied so that there was no possibility 

 of their licking and swallowing either eggs or young maggots. 

 It appears conclusively from these experiments and 

 observations that from eggs laid naturally on the legs of 

 cattle young maggots of Hypoderma bovis bore into the 

 body of che host and become " ripe " in the succeeding 

 spring beneath the skin of the back, also that a bored-in 

 maggot may reach the sub-mucous coat of the gullet-w^all. 

 Such proof of the extensive migrations of the larvae is of 

 special importance in view of the opinion sometimes 

 confidently expressed that only eggs laid on the back give 

 rise to larvae that can complete their development. Eggs 

 appear to be hardly ever laid on the back at all, and we 

 are now assured that maggots which bore in at the he*:! 

 do reach the back and there become " ripe " in readiness 

 to change into the flies of the next summer. 



Royal College of Science, Dublin. 



