1901.] 93 



the skin of cattle, Ji statement supported by further observations in 

 Prof. Brauer's well-known " Monographic tier ffistriden " (18G3), it 

 was generally supposed that the eggs are deposited on the skin of the 

 back and loins, or else attached to hairs in the same region ; and that 

 the young larvae, after being hatched by the warmth of the animal's 

 body, bore their way through the skin, the passage in which after- 

 wards closes up. It was known that for some mouths the larvae lie 

 dormant, or travel about in the tissues of the host, until they 

 eventually come to rest beneath the skin of the back, forming round 

 them the well-known subcutaneous cysts called "warbles." Each 

 warble communicates with the exterior by a hole in the skin, through 

 which the larva breathes, and by means of which it escapes from the 

 host when mature, in order to pupate in the ground. These holes are 

 permanent, remaining when the hide is dressed, and since a badly 

 warbled animal may harbour perhaps a hundred larvae or more, the 

 fiuished hide presents the appearance of having been riddled with 

 shot. Warble-flies are, therefore, the cause of much loss to the 

 leather industry every year. The present paper, however, is concerned 

 with the larva) themselves rather than with their economic importance. 



In the case of Hypoderma linecitum, at any rate, recent investi- 

 gations have shown that the larvae enter the body of the host in a 

 manner different from that indicated above. 



In 1890, Curtice recorded the fact (Insect Life, vol. ii, 1890, pp. 

 207, 208) that in the United States he had found in cattle, during 

 December, 1889, and January, 1890, larvae of what he termed Hypo- 

 derma bo via (really H. Uneatum) in apparently peculiar situations. 

 These larvae, which were "from 10 — 15 mm. long., and 1*5 mm. thick," 

 were situated — 



"(1) in the oesophageal walls, (2) one specimen under the pleura near the 

 eleventh rib, (3) in the subcutaneous tissue of the back, and (1) in subcutaneous 

 tumors which opened by an orifice upon the external skin." 



On the basis of these observations Curtice suggested that: — 



" It is possible tliat the eggs or larva; are licked by the cattle from the backs ; 

 that the larvse make their way into the cjesophageal walls, and from thence, during 

 the proper season, through the back in the neighbourhood of the eleventh rib to 

 the skin." 



The question was further investigated in the case of Hypoderma 

 Uneatum in the United States by Prof, Hiley (Insect Life, vol. iv, 

 1892, pp. 302—317), who fully confirmed Dr. Curtice's views. Prof. 

 Riley's " Conclusions " {op. cit., p. 316), are of sufficient interest to 

 be quoted at length. They are as follows : — 



