Animal Galls. 433 



size. The largest of them are sixteen or seventeen lines in 

 diameter at their base, and about an inch high ; but they are 

 scarcely perceptible before the beginning or during the 

 course of the winter. 



It is commonly upon young cattle, such, namely, as are 

 two or three years old, that the greatest number of bumps 

 is found ; it being rare to observe them upon very old animals. 

 The fly seems to be well aware that such skins will not 



Fly, maggot, and grub of the Ox breeze-fly, with a microscopic view of the maggot. 



oppose too much resistance, and seems to know, also, that 

 tender flesh is the most proper for supplying good nourish- 

 ment to its progeny. " And why," asks Reaumur, " should not 

 the instinct which conducts it to confide its eggs to the flesh 

 of certain species only, lead it to prefer the flesh of animals 

 of the same species which is most preferable ?" The number 

 of bumps which are found upon a beast is equal to the num- 

 ber of eggs which have been deposited in its flesh ; or, to 

 speak more correctly, to the number of eggs which have suc- 

 ceeded, for apparently all are not fertile ; but this number is 

 very different upon different cattle. Upon one cow only 

 three or four bumps may be observed, while upon another 

 there will appear from thirty to forty. They are not always 

 placed on the same parts, nor arranged in the same manner : 

 commonly, they are near the spine, but sometimes upon or 

 near the thighs and shoulders. Sometimes they are at remote 

 distances from each other ; at other times they are so near 

 that their circumferences meet. In certain places, three or 

 four tumors may be seen touching each other ; and more 



2 F 



