NATURAL SCIENCES OF PHILADELPHIA. 369 



oence above; on the lateral base of joints 6 and 7 a semi-oval whitish spot ex- 

 tending to their middle, and a similar spot covering the whole side of the last 

 joint; venter whitish hyaline; anal processes whitish, sometimes with only 

 their middle joint whitish ; seta? whitish, with fuscous incisures alternately wide 

 and narrow. Anterior legs a little longer than the body, with very long tarsi, 

 pale brown, sometimes with the basal half of their femora brown ; the four pos- 

 terior legs paler; all six with a broad postmedian band on the femora, the base 

 and tips of the tibiae, and the tarsal incisures and tips brown. Wings hyaline; 

 veins and cross-veins, hyaline, subequal, moderate, except the three veins of 

 the costa, one discal sector with its basal cross-veins, and sometimes some of 

 the other veins, which are fuscous ; at the discal bifurcation of this sector there 

 is a more or less obvious small brown spot ; subcostal cross-veins fuscous, 

 rather coarse ; a coarse medial black line immediately behind the third vein of 

 the costa, about a millimetre long, and sometimes a slight brown cloud at the 

 costal tip ; posterior wings hyaline, with hyaline veins and cross-veins, except 

 one long and one short series of cross-veins on the basal costa, which are strong- 

 ly fuscous and enclose a brown cloud. 



The 9 differs from the $ as follows : joints 1 5 of abdomen are piceous 

 brown above, paler towards their base ; the anterior legs, as usual in epheme- 

 rinal 9 imagos, are shorter ; and there is no basal cloud on the hind wings. 



Length J 1 12 13,} mill.; $ 12} 14 mill. Alar exp. <-? 25 28 mill. ; 9 

 2829 mill. Setae $ 2024 mill. ; 9 1316 mill. Ant. lg $ 14 mill. ; $ 9 

 mill. Eight tf, two $. 



The subimago, which alone was known to Say, is a very different looking in- 

 sect from the imago ; but having found a specimen drowned in the act of 

 moulting, I succeeded in detaching the subimaginal film from the abdomen and 

 from one wing, thus proving their identity. Say states that in ^ "the ner- 

 vures are brown and margined with brown, more particularly so at the base, 

 middle and tip of their costal margins." This makes, of course, 3 darker 

 clouds on the base, middle and tip respectively of the costal margin, which are 

 more or less plain on all my specimens both $ and 9 > the central cloud al- 

 ways very distinct, the basal one the least so. Dr. Hagen has misunderstood 

 Say's language, and abridging his description says, " veins clouded with fuscous, 

 especially the basal discoidal and apical ones," which would make three fus- 

 cous fasciae. It may be added to Say's description, that the antennal seta is 

 fuscous, the basal joints pale, sometimes tipped with fuscous ; that the $ and 

 9 anterior legs are a shade darker than the posterior ones ; and that besides 

 the femoral bands, the base and tip of the tibiae, and the tarsal incisures and 

 tips, are also brown in all the legs. The abdominal setae are pale brown with 

 brown incisures, pilose at tip ; and the wings are very finely ciliated behind. 



Length 10} 14 mill. Alar exp. 24 32 mill. Seta? 1014 mill. Ant. J 1 

 leg 9 mill. Ant. leg 9 8} mill. Five $, two 9- 



B^etis alternata? Say. tf Piceous brown. The lower } of the eyes, in the 

 living insect, is separated from the upper | by a black line; antennal seta 

 dusky ; epistoma pale. Base of scutel yellowish all round. Sternum a little 

 marked with yellowish. Abdomen with two lateral basal triangular yellowish 

 spots on segments 2 9 or 4 9 more or less confluent, sometimes extending to 

 the dorsum ; on joints 7 and 8 and sometimes on 6, one or both of these spots 

 often enclose a longitudinal brown line and are much elongated ; venter pale, 

 each joint generally with a small central basal spot, two transverse medial dots 

 and an oblique slightly abbreviated lateral line, brown ; joints 1 2 and 8 9 

 sometimes almost brown ; setae whitish with brown incisures ; aual apppndages 

 pale, generally brownish at base. Anterior legs pale brown, posterior 4 almost 

 pale, all with the extreme base and tip and a wide subterminal band on the 

 femora, base and tips of the tibiae and the tarsal incisures and tips, brown. 

 Wings hyaline, glittering, with fuscous veins and cross-veins, the veins rather 

 fine, except the three on the costa which are quite coarse, and the cross- veins, 



1862.] 25 



