﻿- THE CATTLE GRUBS OR OX WARBLES 23 



Hypoderma seldom, if ever, develops in them. Cats are not infre- 

 qiientlj' infested with oestrid larva3, but so far as known these all 

 belong to another genus, Cuterebra. 



Many dogs kept under conditions which would favor an infesta- 

 tion by Hypoderma larvae have been examined with negative results. 

 In one instance three adults of H. liyieatuin were permitted to ovi- 

 posit upon the legs of a dog. About 50 eggs were placed in this 

 way ; although the eggs were viable, no penetration appeared to take 

 place. Unfortunately, the dog was lost before an opportunity was 

 had for the larvae to reach the back. 



Koorevaar (54) found that larvae from the spinal canal of a calf, 

 introduced under the skin of a dog, had migrated extensively when 

 the animal was dissected two weeks later. Some were found in the 

 gullet and some in the spinal canal. 



Four tests of the possibility of the development of H. lineatum 

 in rabbits were made by allowing the flies to oviposit upon the hairs 

 of different parts of the rabbit. Three of these 4 hosts developed 

 lumps on the body within 45 to 100 days after being infested. Some 

 of these had openings through the skin, but the presence of the 

 larvae in them was not definitel}'^ determined, and none persisted for 

 more than a week or two. In one instance several newly hatched 

 larvae of H. Imeatum were introduced into the eye of a rabbit. They 

 were watched for over an hour, but none burrowed into the tissues. 



Two experiments were made with the introduction of larvae of 

 n. lineatum from the gullets of cattle into rabbits. On December 

 22, 1920, 15 larvae measuring from 11 to 15 millimeters in length 

 were introduced into an incision near the left hip joint of a Belgian 

 hare. The rabbit died from infection two days later. Upon dis- 

 section four dead larvae were found, but none of these were far from 

 the point of introduction. 



On November 15, 1922, 10 larvae of H. lineatmn from the gullets 

 of cattle were introduced under the skin of a rabbit on the left side 

 of the back in the lumbar region. The average length of these was 

 14 millimeters. The following morning the rabbit was ill, and had 

 considerable swelling below the point of incision. The infiltrated 

 area extended down the side and under the belly where there was a 

 considerable accumulation of serous material, which was drained. 

 On the second morning the animal was worse, with fever, labored 

 breathing, stiff hind quarters, and an accumulation of puslike ma- 

 terial in the eyes. In the afternoon the animal, which was very 

 low, was chloroformed and dissected. Four living and one dead 

 larva were recovered. Two of these were in the connective tissue 

 from 11/^ to 2 inches from the \Hnnt of introduction. One was on 

 the surface of the large intestine about opposite the kidney, and the 

 fourth was rather deeply imljeddcd in the connective tissue on the 

 inside of the left leg at the knee joint. It was possible to trace this 

 larva with considei'able certainty by an infiltrated path down the 

 side to the median line of the belly, thence backward between the legs 

 and upward to the pin bone, and thence to the inside of the leg, the 

 point at which it was found. Thus this specimen had traveled 6 or 

 7 inches in the subdermal tissue. 



In an experiment carried out by Peter (76'), several larvae were 

 placed undo- the skin of two rabbits. In one of these four living 



