158 Journal New York Entomological Society. t Vo1 - xxvu. 



on the inner edge of the femur of the prothoracic legs (fig. 5) were 

 used to scrape off the particles and transfer them to the mouth parts. 

 A subsequent examination of the stomach revealed the presence of 

 the carmine there. 



When a quantity of material, such as bits of plant tissue, pieces 

 of wood, bark, or silt, was introduced into the stream, the larvae 

 would rear themselves out of their cases far enough to expose the 

 entire thorax, and proceed to comb it with the mesothoracic legs in 

 a single swift stroke. Then the prothoracic legs were used to re- 

 move the material and convey it to the mouth-parts, where it was as 

 eagerly chewed as though it were the daintiest of morsels. Examina- 

 tion of the thorax (fig. 3) shows heavily chitinized pieces on the 

 dorsum of the meso- and meta-thorax, bearing long forward pro- 

 jecting spines which overlap diagonally, forming a sort of meshwork 

 above the thorax at the head end of the case. In-as-much as this 

 habit seems prevalent, only at those times when the water contains 

 a large amount of sediment and fine debris, it seems probable that 

 the primary reason for this action is to keep the passageway open for 

 a good stream of water through the case, and that the food-getting 

 is a secondary matter and quite incidental. 



Through the winter the larvae feed but little, and then on diatoms 

 mainly. With the lowering of the water after the spring freshets, 

 during the middle of April, the larvae fasten their square cases firmly 

 to the stones. Then they feverishly set about spinning a silken 

 sheet of lining, that is perforated in the center, at both ends. These 

 tough cases may persist two or three seasons after the occupants have 

 finished with them. Secure within their cases, the larvae gradually 

 go into a deep sleep and peacefully dream of becoming caddice-flies. 



Explanation of Plate XVIII. 



Brachycentrus nigrisoma Banks. 



Dorsal aspect of larva in attitude of waiting for prey. 



Front aspect of larva in attitude of waiting for prey. 



Diagram of thorax of larva. 



Prothoracic leg of larva three weeks old. 



Prothoracic leg of larva four months old. 



Mesothoracic leg of larva three weeks old. 



Mesothoracic leg of larva four months old. 



Part of comb of mesothoracic leg of larva, in detail, four 



