NEUROPTERA. 233 



These remind one of the cob-houses of our childhood. Fortunately 



the species that make this style of case live in stagnant water, and 

 may, therefore, be kept alive in aquaria. A case closely resembling 

 this in plan but differing in appearance is made of bits of moss. 

 Sometimes leaves are used ; these are either fastened so as to form 

 a fiat case ; or are arranged in three planes, so as to form a tube, a 

 cross section of which is a triangle. 



Whether stones or wood are used, the material is fastened to- 

 gether by silk, which the larvae spin from the mouth in the same 

 manner as caterpillars. In some species the case is composed en- 



Fig. 201. — Case of Caddice-worm. 



tirely of silk. Fig. 201 represents the form of such a case, which is 

 common in Cayuga Lake. 



Before transforming to pupae, the caddice-worms partially close 

 their cases, so as to keep out intruders; but provision is made for 

 the ingress of water for respiration. Thus the owner of the silken 

 case to which reference has just been made, when read}- to trans- 

 form, fastens its case to a stem of the grass which grows in the 

 lake, and then closes the entrance to the case with a lid having a 

 slit-like opening in the centre. The worms making the casus shown 

 in Fig. 199 build a grating in each end of the case. 



It would naturally be supposed that the caddice-worms would 

 escape the attacks of Ichneumon-flies, living as they do beneath 

 water, and within well-built tubes. But this is not so. And curi- 

 ously enough, in certain species at least, the parasitized individuals 

 differ from others in fastening their cases by means of a long band, 

 when about to transform, instead of attaching them directly to the 

 supporting object. 



In the Phryganeidse we find another group which differs in such important 

 characters from the most nearly allied insects that many entomologists bi 

 it should he classed as a distinct order ; and long ago the name Trichoptera was 

 proposed for this order. The rudimentary mouth-parts of the adult eaddice- 

 llies and the structure of the wings separate them from the other Neuroptera, 

 and suggest affinities with the Lepidoptera ; on the other hand, the anal legs of 

 the larva- with hooked claws resemble those of the Sialidae. As indicating the 

 strength of the tendency to recognize the order Trichoptera. it isonly nei 

 to name Hagen, McLachlan, and Brauer as among those that shaie this v iew. 



