302 DIPTERA. 
sion, or plunge at once into the water, 
where the oestrus seldom follows them. 
Lucy. How long do the larvae live on 
the poor cows ? 
Mother, The fly seldom appears till 
June^ and the larvae generally quit their 
abode in Autumn, and immediately bur- 
row in the ground ; their skin then 
gradually thickens, and becomes so hard, 
as to answer the same purpose as the 
outer case of other chrysalids. Within 
this hardened skin the worm in time be- 
comes a nymph; and remains in this state 
till the following summer. 
Lucy, I think, mamma, that the 
maggot's own skin becoming hard, and 
forming the pupa case, is a different 
mode from any you have yet mentioned ;. 
but how does the fly get out of it ? 
Mother, I am much pleased, my dear 
Lucy, by the attention you pay: you are 
very right, this manner of changing to. 
the chrysalis I now mention for the first 
time; but it is common in this order. 
