AQUATIC IX5ECTS IX THE ADIR0XDACK5 561 



Order TRICHOPTERA 

 Caddis flies 



BY COEXELIUS BETTE^s' 



Insects of this order were found to be very abundant at Saranac Inn. 

 Larvae and pupae were ver)" common in Little Clear creek and along 

 the edges of the lakes and ponds of the vicinity, while adults were taken 

 in great numbers by the trap lanterns. Throughout the period of work, 

 swarms of adults, mainly of three species, settled on the hatchery win- 

 dows, having doubtless transformed in the fish troughs. AVhile the ma- 

 terial was therefore abundant, only four species were successfully reared. 

 Of many species the time of transformation did not fall within the period 

 of the work, and consequently a full life histor}' could not be recorded. 



The larvae of these insects, as is well known, build for themselves 

 cases differing greatly in manner and material of construction. Several 

 species of larvae were reared from the tgg, and the larvae were observed 

 to begin making their cases almost immediately after hatching. Before 

 building their cases the young larvae are doubtless at the mercy of many 

 enemies. Hydras were seen killing many of them in rapid succession 

 but were unable to use them as food because of their size. The charac- 

 teristic forms of the cases may be recognized almost from the beginning. 

 The cases are enlarged as the growth of the insect demands. The food 

 of the larvae is doubtless largely vegetable. Several species were ob- 

 served feeding on stonewort, Xitella,and river weed, Potamo- 

 g e t o n , which flourished in the creek. Some species are however 

 known to be carnivorous in their habits. 



Well protected by its case, the body of the caddis fly larva needs no 

 hard covering of chitin. The head and the thorax, with the three pairs of 

 legs, protrude from the case when the larva is moving about or feeding, and 

 these parts are protected somewhat more than the other parts. The legs 

 terminate in one-jointed tarsi, each of which has a single claw. A spur is 

 very prominent at the base of each hook. The abdomen has nine well 

 defined segments and an anal appendage terminated by a pair of hooks 

 pointing outward. These hooks can be fastened into the sides of the 

 case and thus prevent the forcible eviction of the larva. The dorsal 

 side of the first segment is marked by a large protractile tubercle. Two 

 smaller tubercles are located on the ventral side of the same segment. 

 These tubercles are supposed to serve the larva as a means of maintain- 

 ing its position in its case. This view is supported by the fact that a 

 species of Hydropsychidae reared at Saranac Inn constructed no larval 



