﻿38 BULLETIN 1369, U. S. DEPAETMENT OF AGEICULTURir 



Of the three animals receiving the eggs on the legs, one (No. 417) 

 was accidentally killed by a train during the late summer and no 

 examination could be made. In November, larvae first appeared 

 under the skin on the backs of the other two cows (Nos. 167 and 159), 

 and during the fall and winter one of them had 3 larvse to reach 

 the back, while the other had 17. With the animal infested on the 

 shoulders (No. 163), a single larva appeared on the back during the 

 following winter; but it had been observed that many of the eggs 

 on this animal were infertile and had failed to hatch. One of the 

 two animals with infestations on the legs and belly (No. 158) was also 

 killed by a train and not examined, but the other (No. 22) was 

 slaughtered and carefully dissected on July 3. A total of 40 second- 

 stage larvee were found on the viscera and along the gullet. One 

 of the two hosts infested by way of the mouth (No. 414) was dis- 

 sected on November 26 ancl no larvee were found in the gullet or 

 elsewhere. The other animal (No. 160) was observed carefully and 

 repeatedly during the fall and winter and not a single larva came to 

 the back. The two animals (Nos. K23 and 92) receiving the second- 

 stage larvEe through incisions cut near the hock showed 9 and 32 

 larvse, respectively. These appeared along the backs during the fall 

 and winter. 



During the spring of 1921 two heifers were infested by flies which 

 deposited eggs on their hind legs. One of these (No. K23) received 

 about 110 eggs on the feet, but aj)parently none of the 45 eggs 

 hatched which were deposited on this animal on March 3. The first 

 larva came to the back on October 27, and a total of 64 larvse ap- 

 peared during the winter. The other heifer (No. 22D) received 

 far more eggs on the legs but developed only 8 larvse on the back, 

 the first appearing November 9. 



During the season seven bovine hosts were infested by placing, 

 in pockets cut under the skin, larvse of H. llneatiuii removed from 

 gullets of slaughtered animals. Two of the hosts (Nos. 92 and 160) 

 were infested May 3 with larvae (4.5 to 5.5 millimeters in length) 

 inserted above the hock. Each developed an infestation in its back 

 in the fall. The first larva reached the back October 20 or shortly 

 before. Four cattle were infested with 26 gullet larvse per animal 

 on August 26; two received them in the right hind leg, one behind 

 the ear, and one in the back about 8 inches behind the shoulder and 

 3 inches from the spinose processes; this was in order to compare 

 the dates of appearance of larvse on the back and the number suc- 

 cessfully reaching that region. 



One of the two hosts infested on the leg (No. 159) had larvse 

 present on the back on October 17, and at that time the other aninial 

 (No. 167-1) was killed and dissected. On a post-mortem examina- 

 tion 10 larvse were recovered, 3 in the subdermal connective tissue 

 of the back (but no holes had been cut through the hide), 1 under 

 the spleen on the paunch, 1 on the paunch near the esophagus, 

 3 in the mesentery of the colon, and 2 in the submucous tissue of the 

 gullet. One of the latter was near the paunch end of the gullet and 

 measured 13.7 millimeters in length; the other was in the middle 

 of the gullet and measured 11.6 millimeters. Both were headed 

 toward the paunch. 



