36 PROTECTION OF PLANTS, 1917-18 



The mode of dissemination of bots is almost entirely determined by the 

 movement of horses. Therefore, the author can see no reason — unless they be 

 climatic — why the nose-fly should not spread from infested to non-infested re- 

 gions with parasitised -animals. In recent years there has been extensive ship- 

 ping of animals from western provinces to eastern army depots, where the animals 

 are congregated previous to their being re-shipped to Europe and to the picket 

 line. It is quite feasible to suppose, therefore, that this species might become 

 established in the east, if it has not already done so. 



All three species of bot-flies exist in Europe, whence they no doubt originally 

 came to the American continent. Just why the nose-fly did not distribute itself 

 so widely as the other two species is not clear. It may have been that it found 

 eastern environmental conditions imsuitable. But as to whether its absence here is 

 correlated with conditions that are more humid in the east than in the west, as 

 Bishopp suggests (p. 186) is a moot point. At least, the humid atmosphere of 

 England has not entirely checked its activities there. 



Last summer (1917), Dr. Hadwen and the author made an investigation of 

 the three species of bot flies in Saskatchewan, when some interesting results were 

 obtained. These have been incorporated in a paper entitled "A Contribution to a 

 KnoAvledge of Bot-flies, G. intestinalis DeG., G. haemorrhoidalis L., and G. nasalis 

 L.", which the authors expect to be published soon. 



Oviposition. 



The eggs of G. haemorrhoidalis are black and are shaped somewhat like a 

 barnacle. The stalk is grooved and serves to attach the egg to the hair. Contrary 

 to the opinion of Parker^^ the stalk of the egg does not penetrate the skin of the 

 host. The eggs are invariably laid on the hairs of the lip, usually on those of the 

 lower and less frequently on the upper. 



The yellowish eggs of G. nasalis are laid on the rather long hairs of the inter- 

 maxillary region and are not exposed to view. They are elongate ovate and bear 

 two attaching flanges which run almost the whole length of the egg. When there 

 are several eggs on the same hair, they are generally arranged in close series. 



The eggs of G. intestinalis are yellowish white, the clasping flanges running 

 about three-fourths of their length. They are generally exposed to view and are 

 laid indiscriminately over the body of the host, although the species appears to 

 have a decided preference for the long hairs investing the inside of the fore-legs. 



Hatching. 



The conditions favourable to the hatching of the eggs are not alike for all 

 three kinds. Our experiments demonstrated that those of intestinalis require 

 moisture and friction, and we were thus able to corroborate the work of Osborn. 



