17-1 WESTERN QUARTERLY REPORTER. 



Body pale yellowish ; stemmata large, frontal, placed triangularly, 

 two superior ones dusky ; front with a blackish area between the 

 stemmata ; maxillary palpi blackish ; eyes prominent oval ; thorax 

 between the origin of the of the superior wings, with two con- 

 vex, longitudinally oval elevations ; wings nearly equal, pale yel- 

 lowish, a subopake carpal spot near the tip of each; abdomen 

 falcate. 



Length to tip of wings three-fourths of an inch. 



Found near Fort Osage on the Missouri. 



Genus SIALIS Latr. [PERL A Geoffr.— Say, MS. correction.] 



1. S. DORSATA. — Body black, varied with rufous ; labrum pale ; 

 thorax with a dorsal rufous vitta and anterior and posterior rufous 

 incisures. 



Inhabits the Ohio river. 



Head blackish, with about six blacker spots; labrum pale, be- 

 neath pale yellowish ; palpi black ; thorax blackish, with im- 

 pressed blacker lines, anterior and posterior incisures and dorsal 

 vitta rufous, angles rather prominent ; a pale obsolete line from the 

 base of the thorax to the abdomen ; beneath yellowish, disk of 

 the segments black 3 trochanters yellowish; wing nerves deep 

 black ; abdomen black, segments above with yellow posterior 

 margins; venter pale yellow. 



Length to the tip of the wings one and three-fourths of an 

 inch. 



Numerous in May near Pittsburgh. 



2. S. IMMARGINATA. — Body black varied with yellow, or yel- 

 low varied with black ; wings dusky ; nervures brown immar- 

 ginate ; thorax transversely quadrate, posterior angles somewhat 

 rounded, disk somewhat rugose with impressed irregular lines, an 

 impressed dorsal line, on each side of which is a slightly arquated 

 one ; eyes deep black-brown ; all beneath yellow. 



Inhabits the Ohio river. 



Length to the tip of the wings more than an inch ; male much 

 smaller. 



Pupa pale, varied with black ; abdomen annulate with black at 

 thebaseof thesegments; all beneath immaculate; thighs [165] with 

 a black obsolete spot on the exterior tip ; antennae and setae pale 



