THE MUSCIDZ. 403 
describe them, but it must be observed that they do not moult or 
change their skin during their growth, and that when the time for 
metamorphosis is at hand, the body shortens, the skin becomes 
hard, and of a brown colour, and the chrysalis or pupa forms within. 
Many of the larve live as parasites within other insects. 
In the accompanying engraving the larva of Gymnosoma rotun- 
data is shown within the body of one of the Hemzptera. It has a 
long hooked-shaped tube, which is attached to its last segment, 
THE METAMORPHOSES OF Gymnosoma rotundata. 
and this tube is protruded through one of the spiracles or respi- 
ratory orifices of its victim, so that it eats the juices and fat, and 
breathes through the body of the creature or “ host” upon which 
it is parasitic. The perfect insect and the pupa are also depicted. 
The Flesh Fly and the Blue Bottle are very useful as larve, 
or, as they are called, Gentles, for they devour dead bodies of 
all kinds, and many species, belonging to the genus Sarcophaga, 
live upon stercoraceous matter. 
The curious legless larvae are very well known, and so are 
the egg-shaped, dark-brown pupz. The larve, which at first 
A A 2 
