24K Canadian Arctic Expedition, 1913-18 



brown pigment were scattered regularly in the furrows between the body- 

 tubercles (spine-carriers). 



From this latter stage there were all grades of transitions to the dark pupae 

 (pre-pupae) (see below) ; the main colour of the larvae changing gradually from 

 white to a dirty brown, and finally to almost black (post-larvae, pre-pupae), the 

 body tubercles being most strongly coloured in all the larvae; the chitinous parts 

 also become black. In the black-brown post-larvae (pre-pupae) the colour of 

 head, spiracles, and body-spines shades into that of the whole larva. 



A shortening of the larvae now takes place, the terminals being retracted, 

 so that the segments lie telescopically one inside the other. The body-spines 

 and body-tubercles, formerly so pronounced in full grown larvae, seem to shrink 

 in, so that the segments are smoother and the transversal diameter of the post- 

 larvae increases until it is almost as large (about 17 mm.) as the longitudinal one. 

 The larval skin dries and becomes more chitinized and stiffer, so as to protect 

 the pupa inside. Of the post-larvae only six were found in three skins; and the 

 black colour of the pupa shows through its enclosing cyst, though the cyst is less 

 pronounced than in the younger larvae, because the grub lies half-protruded 

 from its exit-hole, hidden by its host's hairs. A few of the exit-holes were already 

 empty (except for the grub excrement) and the cyst inside (formed by the inner 

 part of the caribou-skin around the larvae) had become contiguous to the sur- 

 rounding skin. 



In spite, therefore, of all the annoyance and pain caused by these grubs, 

 it seems that the caribou skins heal quickly after the parasites drop out. By 

 the end of June no grubs are in the skin, the holes they made are almost healed 

 and it may be assumed that the pupae leave the caribou about the end of May 

 and lie on the ground for about a month before the flies appear. Life in the latter 

 stage is probably only short and exclusively devoted to copulation and the 

 laying of eggs on the caribou's hairs, after which the grubs bore through the 

 skin. 



The other dipterous parasite of the caribou is also an oestrid, identified 

 by Mr. J. R. Malloch as Cephenomyia sp. and was noted at the end of May, 

 1916. About twelve grubs 2-3mm long were lying in the nasal passage of the 

 caribou, where they can easily attach themselves by the aid of their mouth- 

 hooks and hang suspended. The smallest ones were white-yellow, with red- 

 brown segmentally arranged spinehooks, black jaws, and anal spiracles. The 

 older ones had the spines darker, and grey-black dot pigment on the dorsal side 

 of the body segments. The oldest ones had still more black pigment (especially 

 behind and ventrally) and still darker spines. Efforts to rear the larvae were 

 unsuccessful. 



This is probably the Tabanus larvae about which Grenfell writes and which 

 he figures in his book on Labrador. The eggs are laid in the nostrils of the 

 caribou, and the grubs probably spend all their time in the nasal, bronchial 

 and oesophagel passages of their host. 



June 1-10, 1916 



A weevil (Lepyrus palustris) was found on June 4, and the first bumblebee 

 (Bombus hyperboreus) was observed. The ponds yielded midge and large 

 dipterous larvae. Some of these latter have a habit of mud-burrowing, but one 

 species seems to be more dependent on air, for it occasionally comes to the 

 surface with the five long, ciliated appendages that surround the spiracles 

 spread in star-like fashion. The adhesion of the surface and the hairy append- 

 ages appears to be sufficient to keep the whole larvae suspended. In this 

 position they may frequently be seen burrowing head first in the mud of shallow 

 water. Dytiscid beetles and a small brick-red water mite were noted. On 

 June 8 three caterpillars, collected at the harbour, were placed for rearing. 

 One, a large naked larva, had evidently been washed out from its feeding ground 



