NEUROPTERA. 433 
| tractile tubes. They construct for themselves fixed places of shelter, 
) more or less imperfect, at the bottom of the water, and against large 
stones, which they leave occasionally for a few moments. Some- 
)times these cases contain many larvae at the same time. Fig. 420 
represents the various states of a Hydropsyche; the larva is seen 
jon the left, the pupa on the right, the winged insect in the middle. 
| Two of the insect’s tents or places of shelter are represented below. 
jig. 421 shows the different states of Rhyacophilus vulgatus, larva, 
}cocoon, pupa, andimago. ‘The genus Rhyacophilus has this pecu- 
larity, that the larva spins itself a cocoon in the interior of its 
\dwelling, before changing into a pupa. 

