= ie 
oe 
_ ie 
THE CATTLE GRUBS OR OX WARBLES 23 
Hypoderma seldom, if ever, develops in them. Cats are not infre- 
quently infested with oestrid larvee, 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 larve have been examined with negative results. 
In one instance three adults of H. lineatwm 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 larve to reach the back. 
Koorevaar (54) found that larvee 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 7. 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 
larvee in them was not definitely determined, and none persisted for 
more than a week or two. In one instance several newly hatched 
larvee of H. lineatum 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 larve of 
H. lineatum from the gullets of cattle into rabbits. On December 
22, 1920, 15 larvee 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 larvee were found, but none of these were far from 
_ the point of introduction. 
On November 15, 1922, 10 larvee of H. lineatwm 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 114 to 2 inches from the point of introduction. One was on 
| the surface of the large intestine about opposite the kidney, and the 
| fourth was rather deeply imbedded in the connective tissue on the 
| inside of the left leg at the knee joint. It was possible to trace this 
| larva with considerable 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 feund. Thus this specimen had traveled 6 or 
| ( inches in the subdermal tissue. 7 
In an experiment carried out by Peter (76), several larve were 
| placed under the skin of two rabbits. In one of these four living 
