430 APPENDIX I 
very rapid in its actions, and consequently not readily seen when 
flying. Its small size and obscure colouring would also prevent 
its detection when at rest in protected places during cold, wet 
days, for it only flies during the dry, warmer days, at which time 
the female attempts to deposit its young larve in the nostrils of 
the sheep. The eggs of the sheep bot-fly are retained until hatched 
in the oviduct, and emerge as young larve or maggots. The 
appearance of one of these flies among a flock of sheep causes con- 
siderable alarm, and they try various ways to prevent it from 
depositing its young larve. They huddle together, lie down and 
bury their noses in the dirt, and even raise a cloud of dust to deceive 
their enemy. When deposited in the nose of the sheep, the young 
maggot, by means of small hooks and spines, begins its migrations 
upward through the nostrils to the frontal sinuses. The move- 
ment of the larva, as it increases in size, greatly irritates the poor 
victim, and it makes many attempts, by sneezing and snorting, 
to rid itself of the parasite. This is rarely accomplished, however, 
until the larva reaches maturity, when it detaches itself from 
the mucous membrane, reaches the nose, and is expelled by the 
violent snorting of its host. 
The grub remains about ten months in the nasal cavity of the 
sheep. After leaving the sheep it pupates and remains in that 
state from four to six weeks, when the adult fly makes its ap- 
pearance. 
Dr. Grenfell informs me that in all of the heads of the caribou 
that he has examined, he has found parasitic larvee, usually just 
below the ethmoid. The injury done the caribou by this parasite 
is not known, nor do we know the species, as neither the larva nor 
fly has been secured. It probably belongs to the genus Cephalo- 
myia. To work out its life history and determine the species 
would prove an interesting subject for investigation. 
The second species infesting the caribou is a subcutaneous para- 
site, which may prove to be the same as the reindeer bot-fly (Hde- 
magena tarandi). Tf not, it is a closely related species, with a 
life history probably similar to that of the ox bot-fly, or warble 
(Hypoderma). The eggs are deposited on and fastened to the 
hairs In a similar manner to those of the horse bot-fly, and always 
in a position within reach of the animal’s mouth, as on the fore 
legs and sides. In licking itself the animal transfers these eggs 
to the mouth, the saliva rapidly dissolves the hard egg cases, and 
the young larve already formed within are liberated. These 
young spiny larvee pass by way of the esophagus through the 
tissues of the animal to the subcutaneous tissue along the back, 
forming large tumours or swellings before reaching maturity. When 
the larva has attained its full size, it bores its way out and drops 
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