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THE INSECT WORLD. 



selves, and so get out. Then they swell till they crack their skin 

 over the back, and the perfect insect emerges. 



The Phryganea pilosa (Fig. 420) is of a yellowish grey, with hairy 

 wings, little adapted for flying. These insects do not eat, and never 

 leave the neighbourhood of the water. During the day they rest on 



Fig. 419. Pupa of Phryganea 

 pilosa, magnified. 



Fig. 420. Phryganea pilosa. 



flowers, on walls, or on the trunks of trees, their wings folded back, 

 and their antennae together. In the evening they fly in dense 

 swarms over streams and ponds. They are attracted by light, as are 

 many nocturnal insects ; and are sometimes found in great numbers 

 on the lamps on the quays in Paris. 



The Hydropsyches (Fig. 421) and Rhyacophili (Fig. 422) are small 

 insects which resemble the Phryganeee very closely. Their larvae 

 have, for the purposes of respiration, some gills, others retractile 

 tubes. They construct for themselves fixed places of shelter, more 

 or less imperfect, at the bottom of the water, and against large stones, 



