332 
Warhle Flies 
squeezed out of the skin by way of control. Later eleven of them 
pierced the skin all along the left side of the back. However, these 
died subsequently, one by one, and were absorbed. On March lOth 
only the punctures which they had made were visible, and all swelling 
had subsided. (Plate XXIV, Figs. 1 and 2.) 
The main object of these experiments was to determine if the second- 
stage larva, taken from the oesophagus and thus interrupted in its 
life-cycle, was capable of completing it in another animal. In Koore- 
vaar s experiments (cited by Carpenter), the larvae were introduced 
beneath the skin of dogs and rabbits, and they were found 14 days 
later in various parts of the body, including the spinal canal and the 
walls of the gullet. Koorevaar therefore concluded that the maggots 
only reach the gullet, or spinal canal, after extensive wanderings through 
the tissues of the ox or calf, and that they do not travel to the gullet by 
way of the mouth. This hypothesis appears to me to be the most 
likely, and the experiment with Calf A given above appears to support 
it. In this exj)eriment the larvae were not seen for a period of eight 
weeks, four of them were then noticed on the calf’s back ; and it is 
certain that they were, during this period, in some unknown part of the 
animal, possibly in the gullet (?). 
In the case of Calf B the larvae were introduced into the calf, and 
their life-cycle interrupted, at a later stage, and it may be that they 
were too far advanced in their development to return to the gullet, and 
not sufficiently matured to migrate to the back. For this reason they 
did not develop fully. It was noticeable that in Calf A two of the 
warbles were larger, and it looked for a time as if they would reach 
maturity. 
In a recent article by Carpenter and Hewitt the authors quote 
Glaser (1913), who states that the newly-hatched larvae he had under 
observation died in one and a half hours if left in dry air, but that within 
an hour after hatching they could be revived by transference to water, 
in which they would live for two days. He concludes therefore that 
they need moisture for their further development and that they would 
obtain this in the gullet. Newly-hatched larvae, placed by him on the 
shaved skin of an experimental calf, made no attempt to bore through. 
One young maggot, however, hatched from an egg laid on his trousers by 
a female H. lineatuni, in June, bored through the skin of his own leg and 
disappeared in one and three-quarter hours, leaving a small round red 
spot visible externally. Four or five days later the larva could be felt 
through the skin, having grown to a length of 2‘5 mm. Then it 
