INVERTEBRATE FAUNA OF LAKE SUPERIOR. 693 



ARTICULATA. 

 INSECTS. 



BIPTERA. 



Many different species of two-winged flies 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, thau in the pure and cold waters of 

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

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

 larvae of the numerous 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 larvae 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 larvae found in the lake. These forms of larvae 

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

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

 distinguished while larvae. . 



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 33 fathoms. Larvae and pupae 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, b. 



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 6 to 8 ftithoms among 

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

 south side of Saint Ignace Island. 



NEUROPTEEA. 



Many species of Xeuroptera, especially of Epliemeridcu and Fhryga- 

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



