AQUATIC INSECTS IN THE ADIRONDACKS 



469 



Strikingly large size, and its habit of flying into houses not unfrequently, 

 and its apparent migrations in numbers, have made it a rather well 

 known species. 



Since the nymph has been described and figured by Cabot, it will suf- 

 fice here to give a brief statement of its more distinctive characters. 



Nymph. Apparently full grown, measures in total length 46 mm ; 

 abdomen 32 mm ; hind femur 7.5 mm ; 

 width of head 10 mm, of abdomen 

 10 mm. 



Body very elongate, widest across the 

 eyes and the seventh and eighth ab- 

 dominal segments. Head flat, much 

 narrowed behind the eyes, with a deep, 

 well rounded concavity on the hind mar- 

 gin, and obtuse hind angles ; labium 

 long extending posteriorly between the 

 bases of the middle legs; mentum 

 (fig. 13) with sides parallel for half its 

 length, then suddenly widened in a regu- 

 lar curve to the bases of the lateral 

 lobes; median lobe with convex front 

 border divided by a shallow open cleft, 

 bearing a fringe of short scales on either 

 side of the cleft ; lateral lobe truncate 

 on tip with a short hook on inner angle 

 at tip, before which are some 12 to 15 

 denticles. 



Abdomen with an obtuse middorsal 

 ridge ; lateral spines on segments q-g, 



• • • , • 1 1 11 FiR. 13 Labium of Epiaesehna lieros 



mcreasmg m size posteriorly, on 9 hardly pabr., from within, piioto by j. g. Needham 

 longer than half of the length of the 



loth segment, but broadly triangular; superior appendage almost as long 

 as the inferiors, not cleft at apex ; laterals half as long, inferiors not quite 

 as long as segments 9 and 10 together. 



AESCHNA 



Three closely related species of this genus are known from the state. 

 Male imagos of these species may be separated by the following key. 



KEY TO SPECIES OF AESCHNA 



a Anal triangle of hind wing of male consisting usually of three cells. Superior 



abdominal appendages of male with a prominent inferior spine at the distal 



end ; genital valve of female strongly elevated at the apex .. const ricta 



aa Anal triangle of the hind wing of the male consisting generally of two cells ; 



superior appendage of the male without jirominent inferior spine; genital 



valve of female not strongly elevated at its apex 



& Superior abdominal appendages of the male with a superior longitudinal 



carina denticulated clepsydra 



Ih Superior appendages of the male with the superior longitudinal carina not 

 denticulated v erti calls 



