114 



THE EEPOET OF THE 



No. 36 



would be a larger opening than the single larva of H. bovis could make, conse- 

 quently a bigger flow of serum. The swellings in the case of H. iovis are some- 

 times quite large, but there is not so much dermatitis or exfoliation of the skin. 



It is clear that the amount of damage done would depend on the variety 

 of bacteria introduced beneath the skin, and to the resistance of the animal 

 against the particular organism. 



One remarkable fact I have noted which applies to both species of larvae, is 

 that the swellings and skin lesions are confined almost entirely to the older animals, 

 the calves only show slight effects. This peculiarity can be observed in several 



Lesions on outside of cow's leg. 



Lesions on hindquarters; note large 

 swelling on left leg behind the 

 udder. 



microbial diseases. It is a sort of natural immunity which breaks down as they 

 grow older, and is all the more interesting because young cattle are more para- 

 sitized than the old by Warble flies. 



No appreciable lesions have been noticed below the k^ee or hock. The skin 

 while it is very thick on the legs, is quite porous and open; perhaps owing to 

 its tightness and thickness the swellings are not so evident. H. Iovis does not 

 lay as many eggs round the hoof as E. Uneatum. This is an important difference, 

 for it is probable that many of the lamenesses resulting from swollen feet are due 

 to the larval penetration. For three years in succession, lamenesses among the 

 cattle have occurred here during the season for H. Uneatum. 



Situations in Which Eggs aee Laid. 



There is little to add to my previous descriptions, except to emphasize the 

 irregular distribution of eggs as compared to H. Uneatum. The photographs 

 show the scattered lesions. The irregularity must be due to the fact that cattle 



