S. Hadwen 
337 
a time its movements ceased. Another attempt was made later with 
two larvae of H. bovis. These also hatched six days after the eggs were 
laid. The experiment was again unsuccessful; one larva, as in the 
preceding case, made no effort to penetrate the hide, while the other 
made an attempt and then was unfortunately lost. Whether it was 
brushed off by the calf or not, I cannot say. 
Hypoderma bovis. 
The first time the cattle were really seen to “ gad ” was on May 31st, 
and on this date the first capture of H. bovis was made. By noon all 
the animals were exhausted. It was suspected that H. bovis was the 
cause of the trouble, and later a single female was caught. 'After the 
fly was captured the animals remained tranquil for the rest of the day. 
On June 2nd the animals were again running about the paddock 
terrified. A fly was captured and the animals were then shut up. 
A small calf, which had never been outside before, was tied to a post, 
and the fly was liberated near it. It struck the calf a number of times 
and finally the animal became so terrified that it lay down. The same 
thing has happened several times this season with the animals which 
were loose in the paddock. This paddock is small and there is no 
shelter provided for the cattle, so that if the flies are numerous the 
animals finally become so tired and stubborn that they lie down ; they 
behave in exactly the same way as cattle which are reluctant to be 
driveir. Once or twice I have seen H. bovis attack them when they were 
lying down. Oviposition in this case occurred on the flanks and round 
the buttocks. This year I have seen H. bovis ovipositing higher up 
on the host’s body than I ever did before, and have secured several eggs 
which were laid on the rump, near the root of the tail. In 1912 no 
eggs were discovered above the stifle-joint. 
Flies were very numerous during the month of June, and on the 
10th five specimens were caught with the net during the day. A 
curious observation was made on this day. One of the flies which had 
been caught a few minutes before, was placed on a calf’s back, the net 
being held above it to prevent its escape ; it had not been on the animal 
for more than a minute, when it was seized with a kind of spasm and 
died instantaneously, the whole body becoming rigid immediately after 
death. This observation is recorded because another fly had died in 
the same manner in a previous experiment. In neither case had the 
insect been injured during capture. The warble fly appears to be a 
delicate insect which cannot stand much handling, and in this it 
