A CONTRIBUTION TO THE KNOWLEDGE OF BOT-FLIES. 101 



■denticles and scales, which cannot fail to advance the efforts of the larva, once it 

 has effected an entrance. 



Since the completion of these experiments, we find that Koubaud (3) has demon- 

 strated that a larva, hatched from eggs sharply brushed by the lips of a guinea-pig, 

 immediately burrowed beneath the buccal mucosa in the animal's mouth and 

 maintained itself parallel to the surface in travelling towards the throat. Its course 

 was followed for a period of nine days, when it had then attained a size approximately 

 equal to that of the larva just previous to the first moult. From this it is inferred 

 that the infestation of the horse is produced when, for some reason or other, the 

 animal rubs the eggs with the buccal membranes of its lips. The author goes on to 

 state that in cases of " creeping myiasis " due to bot-larvae, entrance is not apparently 

 made directly through the epiderm, but by way of the exposed mucous membranes of 

 the eyelids and lips, or of some skin lesion. Regarding his statement that larvae 

 are unsuccessful in penetrating the skin of the horse, wet or dry, and die very rapidly, 

 the negative results in our own observations of the larvae on fresh skin removed from 

 horses, bear him out. 



Hall (12) has recently succeeded in obtaining some interesting results regarding 

 incidental myiasis of bots in dogs. Bots, according to this author, have been found 

 on a few occasions in the stomachs of dogs, the infestation probably arising from 

 the eating of bot-infested stomachs of horses. In his experiments, 6 specimens each 

 of G. intestinalis and G. nasalis, enclosed in gelatine capsules, were fed to each of 

 two dogs. Three specimens of the former succeeded in establishing themselves 

 for a period of 35 days, after which the animal was killed and examined. They 

 were found to have settled in such diverse locations as the stomach, the caecum 

 and the lower part of the small intestine. The specimens of G. nasalis did net succeed 

 in establishing themselves, and none were found on post-mortem examination. 

 Negative results were also obtained in another experiment with the larvae of 

 G. haemorrhoidalis, although the same animal retained one of six larvae of G. intes- 

 tinalis, fed at the same time, for as long as 13 days. The author quotes the parallel 

 results of Raillet, who worked along similar lines. 



It would be irrational to attach too much value to these experiments of Hall and 

 Raillet. It has been our experience that the mature larva of bots will attach them- 

 selves very readily to animal tissue of various kinds, and it is only natural to suppose 

 that they will endeavour to fix themselves temporarily to the walls of the alimentary 

 canal of any strange mammalian host. The fact that several of the larvae in Hall's 

 experiments were passed per anum soon after they were fed to the dogs, seems to us 

 to prove that their unaccustomed environment did not suit them. 



Distribution in Canada. 



So far as our information goes, G. intestinalis occurs in Ontario, Alberta and 

 Saskatchewan, as well as in British Columbia. It is more than probable that it is 

 present throughout Canada wherever its host is found. G. nasalis occurs in the 

 three western provinces, Saskatchewan, Alberta and British Columbia ; while 

 G. haemorrhoidalis has been taken in Manitoba, Saskatchewan and Alberta. In the 

 opinion of F. C. Bishopp, of Dallas, Texas, who writes under the date of 12th February 



