﻿22 BULLETIN 1369, U. S. DEPARTMENT OF AGEICULTURE 



2 larvse appeared on the back December 12, also in the lumbal' 

 region. Each larva had cut a hole through the skin, and from these 

 holes there was an extensive discharge of serum which hardened, 

 matting the hair over the grub, thus indicating a marked reaction 

 on the part of the host against the larvae. All evidence of the 

 presence of the larvae disappeared in a few days. 



During 1922 H. E. Cross forwarded a series of Hypoderma larvse 

 from goats on the Punjab, India. Most of these proved to be H. 

 crossi Patton, but there were two larvae of H. Uneahmi, one in the 

 fourth and one in the fifth stage. 



Peter {76) placed 45 larvae, removed from the spinal canals of cat- 

 tle, under the skin of two goats ; a single larva finally completed its 

 development. 



Koorevaar {54-) showed that it is possible for larvae of H. hovis 

 to complete development in a goat after their removal from the 

 spinal canal of cattle and introduction under the skin of the goat. 



Brauer (6') records .sheep (Ovis aries) as a host for Hypoderma 

 larvae, stating that Winnertz had seen a number of flies following a 

 flock and that Schwabs asserted that grubs occur under the skin of 

 shorn sheep. These he pronounced to be H. hovis. It is noteworthy 

 that Brauer placed a question after Ovis aries as a host. The writers 

 have never observed a larva of Hypoderma on a sheep in nature, nor 

 have they seen any indication of the attack of sheep by heel flies. 



The writers have carried out a few experiments to illustrate how 

 larvae will develop in sheep. The flies seem averse to laying eggs on 

 the wool, but oviposit readily on the hairs of the legs. Forty eggs 

 attached by a fly above the hoof of a sheep apparently did not hatch, 

 or at least no lesions indicating penetration were observed. These 

 eggs were known to be viable. During the spring of 1922 about 75 

 eggs were deposited on the legs of a sheep ; subsequent examinations 

 failed to indicate that hatching or penetration had taken place. 

 Some of the eggs of this lot were known to be fertile. During the 

 spring of 1923 at lea.st a few eggs of a number deposited on the leg 

 of a sheep hatched and the larvae penetrated, as indicated by the 

 presence of lesions. 



Two grade Shropshire sheep were infested November 29, 1922, 

 by inserting under the skin a few inches above the right hock 20 

 H. lineatmn larvae averaging 13.2 millimeters in length, taken from 

 cattle gullets. These were probably all second-stage larvae when in- 

 troduced. On December 7 one larva appeared on the back of one 

 of the sheep, and on December 9 one came up on the other host. 

 Larvae continued to reach the subdermal tissues of the backs of both 

 sheep at intervals of a few days until January 3, 1923, when a total 

 of 11 had reached the back of each animal. They were rather gen- 

 erally distributed over the backs, but more numerous in the lumbar 

 region. There was more or less exudate from the grub holes, and in 

 no case did the larvae remain longer than about 10 days before suc- 

 cumbing. Several dead larvae, all in the fourth stage, were found at 

 different times in the wool. 



Many j^eople are of the opinion that Hypoderma larvae are to be 

 found in small domestic and wild mammals. There are no published 

 records of such occurrence in nature, and the examination of many 

 small mammals in the course of the work leads to the belief that 



