INVERTEBRATE FAUNA OF LAKE SUPERIOR. 693 



AETICULATA. 

 INSECTS. 



DIPTERA. 



Many different species of two-winged flie-? in the larva stage inhabit 

 the waters of Lake Superior. The great majority of the species, how. 

 ever, inhabit only the shallower waters, and are never found below the 

 depth of a few feet; and such species are very much more abundant in 

 pools, marshes, &c., in the vicinity, than in the pure and cold waters of 

 the lake itself, where, it seemed to me, there were much fewer of all 

 kinds of insect larvte than in the lower lakes. The slender worm-like 

 larviB of the nnmerous species of Chironomus were not uncommon in 

 dredgings.even from great depths, and some of the species apparently 

 live in abundance over the entire bottom of the lake. The species of 

 the genus seem to be very generally diffused ; the larvie of some of the 

 species even inhabiting salt-water. The winged insects themselves are 

 delicate, mosquito-like flies, with plumose antennae, and often swarm in 

 vast numbers about ponds and marshy ground. I mention a few of the 

 different forms of these larvie found in the lake. These forms of larv;ie 

 may each, very likely, represent several species in the adult state, bat 

 for the present purpose it is convenient to speak of forms which can be 

 distinguished while larvoe. 



Chironomus, species, a. (Plate III, figs. 20, 21.) 



A large opaque-white larva and its pupa were common in all the shal- 

 lower dredgings and down to 32 fathoms. Larvae and pupje of appar- 

 ently the same form were found in the stomachs of white-fish taken at 

 Sand Island and at Sault Sainte Marie. 



Chironomus, species, h. 



A semi-translucent larva, much more slender than the last, was found 

 in many of the shallow dredgings, and was often common, even down to 

 147 fathoms. The same form was found in abundance in the stomachs 

 of white-fish taken at Outer Island. 



Chironomus, species, c. (Plate III, fig. 22.) 



A small entirely blood-red larva occurred in G to 8 fathoms among 

 the Slate Islands, and in 8 to 13 fathoms among Cladophora, &c., on the 

 south side of Saint Ignace Island. 



NEUPtOPTERA. 



Many species of yeuroptera, especially of Ephcmeridw and Phryga- 

 neidce, are found about the lake, but, as in the case of the Diptera, most 



