456 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 larvae in the nostrils of 

 the sheep. The eggs of the sheep bot-fly are retained until hatched 

 in the oviduct, and emerge as young larvae 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 larvae. 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 larvae, 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 (GEde- 

 magena tarandi). If 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 larvae already formed within are liberated. These 

 young spiny larvae pass by way of the oesophagus 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 



