MUSCA. 87 



The Piloses have a few hairs, chiefly on 

 the thorax, and their antennae are either 



Plumatce or 



Setaria. 



" In the morning of the ninth of September," 

 says Leeuwenhoek, " I found 145 eggs laid as 

 I judged by one fly. Some of these eggs, with 

 a piece of dried flesh, I put into a glass, and 

 carried in my pocket, the weather being cold, 

 to see in what space of time maggots would be 

 produced, and I found some of them the very 

 same day. The next morning all the others 

 were hatched ; and I found that, in one night, 

 they had all grown twice the size of the eggs." 



The rapid multiplication of the fly is thus 

 calculated by the same author. u Let us sup- 

 pose that in the beginning of June there shall 

 be two flies, a male and female, and the female 

 shall lay 1 44 eggs, which eggs in the beginning 

 of July shall be changed into flies, one half 

 males and the other half females, each of which 

 females shall lay the like number of eggs ; the 

 number of flies will amount to 10 3 000 : and 

 I % 



