378 PROCEEDINGS OP THE ACADEMY OF 



The rj 1 9 subimago differ only in the usual manner from the imago. One 

 d\ one 9. 



Ephemekella consimilis, n. s. $ Differs from the preceding chiefly in the 

 great elongation and narrowness of the mesothorax, its anterior lobe or prae- 

 scutum being half as long again as wide, and the whole mesothorax being four 

 or five times as long as wide ; whereas in excrucians the anterior lobe is 

 scarcely longer than wide, and the whole mesothorax is scarcely three times 

 as long as wide. The sternum is ferruginous, and the legs are immaculate, 

 except the tips of anterior tibia and the first tarsal joint, which are fuscous. 



Length rp 5 mill. Alar exp. $ 14 mill. Seta $ about 5 mill. One $, which 

 has both the left and the intermediate seta remaining ; 9 > unknown. 



B^tisca. New Genus. 



Wings four ; front wings with numerous cross-veins ; costal cross-veins, 

 except the basal one and those on the terminal one-third of costa, scarcely 

 visible, entirely absent on the middle of the costa ; terminal veinlets distinct, 

 not branching from the veins, but partly connected with them by cross-veins. 

 Hind wings wide, with numerous veins, and except towards the tip with 

 numerous cross-veins ; tip with many isolated veinlets. Eyes $ contiguous, 

 simple. Body very robust ; middle piece of prosternum deeply and very 

 widely emarginate behind ; anterior mesothoracic lobe not nearly half as long 

 as wide, and transversely truncate ; mesothoracic scutel very large, horizon- 

 tally extended so as to attain the tip of the first abdominal joint. Fifth 

 abdominal joint twice as long as any of the others, which are subequal. 

 Setae three, exterior ones short, middle one rudimental, distinct, exarticulate. 

 Tarsal structure as in Bcetis subgenus B. 



B^tisca (Bcetis) obesa, Say. Undescribed imago. ^ Ferruginous -piceous. 

 Each side of the epistoma with a divergent basal elliptical carina, confluent at 

 its base with the central carina ; antennas ferruginous, seta generally pale, 

 sometimes fuscous at base. Sternum paler behind, especially the space 

 between the posterior coxae. Abdomen paler, sometimes quite pale, with the 

 tips of the joints whitish ; anal processes pale, sometimes fuscous at tip ; setae 

 whitish, with regular fuscous incisures at base, which generally disappear 

 towards the tip ; intermediate seta ferruginous, about half a millimeter long. 

 Legs pale greenish-yellow, anterior legs with the knees and the tarsal inci- 

 sures and tips slightly fuscous ; hind legs with only the tarsal tips cloudy. 

 "Wings hyaline, the veins fine, except the three costal veins which are rather 

 coarse ; the cross-veins so fine as to be invisible to the naked eye except on 

 the costal tip, where they are somewhat coarser, and except also the oblique 

 basal cross-vein, which is particularly coarse ; costal veins yellowish, the 

 the third vein piceous at its extreme base ; a few of the principal veins 

 slightly tinged with fuscous, the rest, as well as the cross-veins, hyaline. 



The 9 only differs from <$ in the vertex being varied with ferruginous. 



Length J 1 V 8 mill.; 9 68 mill. Alar exp. tf 2022 mill. ; 9 2224 

 mill. Sela $ 6 1 mill. ; 9 e ? mil1 - Aat - le *S C? 8 2 mil1 - > 9 (same size,) 

 4 mill. Twenty J 1 , ten 9. 



The subimago, which alone was known to Say, and from which I have ob- 

 tained the imago, differs from the imago in the colors being darker and obscu- 

 rer, and in the wings being " dark-brown, with numerous small, transverse, 

 hyaline [spots or abbreviated lines, and a large hyaline,*] very oblique, semi- 

 fascia about the middle on the anal half." Tnere is also another large, oblique 

 hyaline semifascia at the costal tip, and, as Say adds, the hind wings, except at 

 tip, have numerous transverse, abbreviated, hyaline lines. The setae are ob- 

 scure green, with fuscous incisures. One specimen, captured a month before 



* The words included in brackets [ ] are omitted in the reprint of Say's Works. 



[Sept. 



