358 



INSECT ARCHITECTURE. 



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 



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



will not oppose too much resistance, and seems to know, 

 also, that tender flesh is the most proper for supplying good 

 nourishment to its progeny. " And why," asks Eeaumur, 

 " 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 prefer- 

 able?" The number of bumps which are found upon a 

 beast is equal to the number of eggs which have been depo- 

 sited in its flesh ; or, to speak more correctly, to the number 

 of eggs which have succeeded, for apparently all are not 

 fertile ; but this number is very difterent 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 cir- 

 cumferences meet. In certain places, three or four tumors 



