WESTERN QUARTERLY REPORTER. 171 



Length to the tip of the wings one-half inch; of the body 

 three-tenths of an inch ; of the superior wings nine-twentieths 

 of an inch ; of the antennae three-tenths of an inch. 



This species appears in vast numbers early in May on the river 

 Ohio. From the 7th to the 9th of that month, when descending the 

 river, I observed them near each shore, flying [161] in opposition to 

 the direction of the wind, and so extremely numerous that, hav- 

 ing a white appearance when flying, they might be compared to 

 flakes of snow, in a moderate fall of that meteor. They were 

 most numerous on the 7th, and appeared to decrease in number 

 daily. 



3. P. lateralis. — Body blackish ; wings white ; superior 

 wings spotted with brown ; eyes dark reddish-brown ; feet 

 white. 



Inhabits Shippingport. 



Body blackish with cinereous hairs above, and shaded with 

 plumbeous beneath ; eyes prominent, dark reddish-brown ; antenna) 

 and mouth pale; thorax black, with cinereous hairs; pectus 

 black, slightly cinereous or plumbeous ; feet whitish ; wings 

 white ; superiores slightly spotted with brown, a common spot 

 on the middle of the inner margin, and several nearer the tip, 

 somewhat arranged into a band, the costal one of which is larger; 

 inferiores white immaculate ; abdomen blackish, pale vitta each 

 side, and a pale posterior margin to the segments ; caudal appen- 

 dages white. 



Length to the tip of the wings two-tenths of an inch ; of the 

 body two-tenths of an inch; of the antennas three-tenths of 

 an inch. 



This species appears in very great numbers on the banks of 

 the Ohio, near Shippingport, on the 21st of May. Judging 

 from the small space of about half a mile on the Indiana side of 

 the river, where I had an opportunity to see them, their numbers 

 could be little inferior to that of P. numerosa, which occurred a 

 few days before, but of which a specimen was now rarely seen. 



4. P. semifasciata. [Ante, p. 97.] 



Genus BAETIS Leach. [162] 



1. B. PEMORATA. — Wings whitish ; nervures deep brown, and 

 marginated with brown ; inferior wings subovate, hardly half as 

 long as the superior ones. 



