^"22 HYMENOPTERA. 
LiUcy. A toothed sting would give a 
terrible hurt. 
Mother. They very seldom attempt 
to use their saws for stinging ; each of 
them have in fact two saws, placed so 
close together as to appear only one, un- 
less examined through a microscope, and 
observed at the time the fly is at work. 
Lucy. How does it use them ? 
Mother, While one saw is thrust for- 
ward the other is drawn back, and by 
this alternate movement double work is 
performed. 
Lucy, Like the two dashes in the 
double pnmp churn, one up, and the 
other down. 
Mother, That is, they move alter- 
nately, or one after the other in constant 
succession. 
One species of these flies does a vast 
deal of mischief in spring, when the fruit 
is setting; it pierces a little hole with its 
saw, and drops its diminutive egg into the 
new formed fruit, which a tiny caterpillar, 
quickly issuing from the egg, begins to 
