148 



HALF HOURS WITH INSECTS. 



[Packard. 



Fig. 111. 



lar-like body is provided with white, slender filaments, aris- 

 ing in groups of from two to five and crossing over the back 

 of the worm. When the case worms are about to transform 

 they close up the mouth of their case with a 

 grating, or, as in the snail-like case-worm 

 (Helicopsyche), wliose case (Fig. Ill) is made 

 of grains of sand, they close the aperture by a 

 dense silken lid, pierced by a slit through 

 which the water enters. The only exception 

 known to this mode of respiration in the large family of 

 Caddis flies is Enoicyla, which is terrestrial, living in moss 

 at the roots of trees, and consequently has no respiratory 



Fig. 112. 



Nemoura and pupa. 



filaments. Notwithstanding the submerged life of these 

 case worms, they are attacked by ichneumon flies when in 

 the larval state. How the young ichneumon lives in the 

 submerged body of its host is not known. 



The branchial gills in the Perla and its allies, Nemoura 

 (Fig. 112, and pupa) and Pteronarcys, etc., which are flat- 

 bodied insects living under stones in streams, have been in- 

 vestigated by Newport, the famous English anatomist, and 

 quite recently by Dr. Gerstaecker of Berlin. Mr. Newport 

 made the astonishing discovery that the Avinged adult Ptero- 



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