PARNIDAE. 115 



Sub-Family I.— PSEPHENIDAE. 



The only member of this sub-family known is Psej)henus Le- 

 contei Hald., a flattened, blackish, finely pubescent insect, with 

 testaceous legs, found in the Middle States, on bushes overhang- 

 ing streams. It differs remarkably from the other members of 

 the family ; but the other two sub-families are also distinguished 

 by so many characters, that I prefer regarding this also as a 

 sub-family, to placing it as distinct. 



The head is free, not retractile ; the mouth inferior ; the max- 

 illary palpi very long, gradually dilated, the last joint securiform; 

 the anterior part of the front is very prominent, and the upper 

 face concave ; the antenna? are inserted at the sides of the front, 

 distant, longer than the head and thoi'ax, serrate ; the eyes are 

 large, convex, finely granulated. The anterior coxae are large 

 and globular, the coxal cavities prolonged externally, showing a 

 very large trochautin ; the presternum is carinate, and its poste- 

 rior process is long and narrow; the mesosternum oblique, chan^ 

 nelled ; the side pieces of the metasternum are wide, and the 

 epimera visible ; the posterior coxae dilated into a plate ; the 

 epipleurae are narrow, and continue to the apex; the abdomen 

 has seven ventral segments, the first and second connate, the fifth 

 broadly emarginate, the sixth deeply bilobed, only visible around 

 the cmargination of the fifth, seventh rounded, entire, filling the 

 emargination of the sixth. The body is clothed with the same 

 line pubescence that characterizes the other sub-families, enabling 

 a film of air to be preserved beneath the water. 



The larva is an elliptical object, with the margins widely ex- 

 tended beyond the body, and is seen on stones under the water of 

 rapid streams; it is especially abundant in the rapids of Niagara, 

 and differs in no important particular from the larva of Helichus, 

 of the next sub-family. It respires by branchial filaments. 



Sub-Family II.— PARNIDAE (gcnuini). 



The anterior coxae are transverse, with a distinct trochantin; 

 the posterior coxse dilated into a plate; the abdomen has five 

 ventral segments, the fifth rounded at the tip ; the front is not 

 prominent, as in Psephenidae, and the oral organs are anterior; 



