148 
HALF HOURS WITH INSECTS. [Packard. 
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 
(Helicops 3 T che), whose case (Fig. Ill) is made 
of grains of sand, they close the aperture by a 
Case of dense silken lid, pierced by a slit through 
Heiicopsyche. w hi c h the w T ater 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 . 
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 winged adult Ptero- 
20 
Fig. ill. 
