V CADDIS-WORMS 265 



Caddis-worms. The tracheal gills may be numerous 

 and unusually large, or altogether absent. The anal 

 feet are unusually long and powerful, two-jointed, 

 and armed with strong hooks for grappling. Just 

 before pupation, the larva constructs a pupal case 

 of stones firmly fastened together. Enclosed in this, 

 its respiratory requirements are much the same as 

 those of ordinary Caddis pupae. Accordingly tracheal 

 gills, if not present earlier, now appear, and the sides 

 of the abdomen are extended laterally by processes 

 which resemble, in their effect at least, the ordinary 

 lateral fringes. 



I am indebted to Mr. T. H. Taylor for the follow- 

 ing interesting particulars respecting the mode of 

 life of the larva of Plectrocnemia : — 



" Plectrocnemia finds its home in streams where 

 the water flows swiftly over a stony bed. If a stone 

 be lifted out, the under side is often found to be 

 covered with patches of mud from which brown larvai 

 emerge and begin to crawl over the surface. The 

 muddy particles are evidently held together by some 

 binding substance, and the whole forms the retreat 

 of the Caddis-worms, corresponding to the cases of 

 Phryganea. When a larva is placed in a vessel 

 of clear water, it at once begins to explore its 

 new quarters, and eventually selects a site for its 

 dwelling. This is made of silken threads secfeted 

 by the large silk glands, and when completed the 

 structure consists of a tube considerably longer 

 and broader than its occupant, and open at both 

 ends. It is supported and strengthened by a mesh- 

 work of silken threads, which spread out for a 



