772 Notes on the Cases of some South Brazilian Trichoptera. 



they are widened in the middle, corresponding to the increasing thickness of the 

 abdomen of the larvae; from one end there proceeds a string of silken threads, 

 generally about as long, but sometimes even more than twice as long as the 

 cases, by which the latter are fastened to the upper side of stones. Thus the 

 larva is secured against being carried away by the current, and at the same time 

 by the mobility of its case its pasture ground is greatly enlarged, and the more 

 so as it can issue indifferently at either end of its tube. It feeds on microscopical 

 algae. Before its change the string is much shortened and thickened, being thus 

 transformed into a rigid footstalk, able to sustain the case in an upright position. 

 The case of the pupa is somewhat compressed, oval or club-shaped, rounded at 

 the upper, attenuated at the lower, end. The pupa emerges, for its final trans- 

 formation, at the upper end of the case. 



Genus VI. Peltopsyche. 



The larvae live in larger tributaries of the Itajahy, preferring rapids. One 

 species (P. Maclachlani) has as yet been found only in one single rapid near the 

 mouth of the Warnow. The cases resemble in shape, colour and size the well- 

 known egg-cases of Nephelis, and are fixed, often in very large numbers, to the 

 upper side of stones; they are made of a brown, rather tough, coriaceous sub- 

 stance. Their upper wall forms a rather flat elliptical shield, smooth in P. Macla- 

 chlani, transversely striated in P. Sieboldii; the basal wall is very thin, and firmly 

 glued to the underlying stone, so that it can hardly be separated without being 

 torn. At either end of the case there is a small circular opening. In most 

 Hydroptilidfv the abdomen of the older larvae is much swollen ; in Peltopsyche it 

 is so in a quite extraordinary degree, filling nearly the whole case. The very 

 slender anterior part of the body is bent and hidden beneath the huge abdomen, 

 of which it appears to be only an insignificant appendage. The pupao are 

 remarkable for the unusually great difference which the complicated corneous 

 patches on the back of the abdomen show in the two species. The perfect in- 

 sects differ from all known Trichoptera by the antennae of the d, some of the 

 basal joints of which are produced into long processes exhibiting a complicated 

 structure, very different in the two species, and which I have not yet been able 

 to unravel in a satisfactory manner. From what I have seen, I am led to sup- 

 pose that these strangely modified basal joints of the antennae may be odoriferous 

 organs. 



