284 Scientific Proceedings, Royal Dublin Society. 



of the cuticle, as in the ease of the larva of Gastrophilus. This fact may 

 have a bearing on the conditions under which the young Hypoderma larva 

 has to live. 



We hope that before long these conditions may become well known. The 

 gap in our knowledge with regard to the life-history of Hypoderma is 

 between the hatching of this little spiny maggot and the appearance of the 

 small second-stage maggot in the gullet-wall. Is the maggot's path of 

 entrance by way of the mouth, or does it bore through the skin ? Sug- 

 gestions and observations with regard to this question may be found in the 

 useful summary of Imms ('06). 



All the maggots of H. bovis which we saw died quickly after hatching 

 amid their unnatural surroundings in the incubator. Glaser ('13, p. 34) 

 states that those under his observation died in one and a-half hours if left 

 in dry air ; but that within an hour after hatching, they could be revived by 

 transference to water, in which they would live for two days. He concludes, 

 therefore, that they need moisture for their further development, and that 

 they would obtain this in the gullet. Newly hatched larvae placed by him 

 on the shaved skin of an experimental calf made no attempt to bore through. 

 One young maggot, however, hatched from an egg laid on his trousers by a 

 female E. lineatum in June, bored through the skin of his own leg, and dis- 

 appeared in one and three-quarter hours, leaving a small round red spot 

 visible externally. Four or five days later the larva could be felt through 

 the skin, having grown to a length of 2'5 mm. Then it apparently worked 

 its way upwards, for early in September swellings were apparent on the hip 

 and abdomen, and at the end of that month a swelling in the lower end of 

 the gullet was indicated by pain when swallowing. This moved quickly up 

 the gullet, and on October 2ad Glaser had the satisfaction of extracting a 

 Warble-maggot 7*5 mm. long (a common size of larva to be found in an ox's 

 gullet) from his own mouth ! 



This involuntary experiment tends to show that a Warble-larva can bore 

 through the skin of the leg and work its way into the gullet in the human 

 subject, and that the insect might pursue the same course in the ox. As 

 mentioned in the introduction to this paper, the experiments with muzzled 

 calves tried during several years at Ballyhaise show that animals apparently 

 unable to swallow either the eggs or young larvse of Hypoderma are at the 

 most but partially protected from infection. The strong mouth-hooks and 

 piercer, and the well-developed spiny armature of the newly hatched maggot, 

 suggest that it could, perhaps, bore as readily through the skin as through 

 the mucous coat of the gullet, and we may eventually find the former to be, 

 after all, the usual mode of entrance. 



