368 TRANSFORMATIONS OF INSECTS. 
soft skin of the abdomen is terminated by two hooks, which 
anchor the insect in its dwelling. 
When about to undergo their metamorphosis the larve fix 
their tube or case upon something and close up the ends. The 
nymphs have the same kind of respiratory organs as the larve, 
and in order to enable its successor to breathe, the larva closes 
the tube with a sort of open-work fence, which, whilst it prevents 
any intrusions, allows the water to flow in and out. 
The nymph has rudimentary wings, and resembles the larva 
more than the imago. 
Hydropsyche atomaria. 1ARVA, IMAGO, SHELTER, PUPA, AND CASE. 
The caddis fly, with yellow or fawn-coloured antenne (PAry- 
ganea flavicornis), when in the larva state, forms its case with large 
bits of wood. Pkryganca rhombica chooses the sprigs of aquatic 
plants, and Pkryganeca fusca makes a central tube of tiny pieces 
of stone, and adds long straws and shreds to the outside. 
The tubes of these species are represented in the engraving. 
Some caddis flies, when in the larval state, form shelters which 
are not movable, and which afford homes to several individuals. 
The species of AHydropsyche have larve with branchial filaments 
or gills attached to the abdomen, and their metamorphosis into 
the pupa is complete. 
