No. 433.] 



UNKNOWN EPHEM ERID NYMPHS. 



29 



in outline, their mid-veins extended into slender filaments, 

 which are nearly as long as the gill leaf proper (Fig. 2, b) ; the 

 gills gradually become smaller and more slender posteriorly, 

 until on segment 7 they are lanceolate (Fig. 2, c). Veins red- 

 dish, thick, passing abruptly into very fine branches. 



Callibaetis ferruginea Walsh. 

 Imagos of this species have been taken from Canada to the 

 southern states ; none are recorded from New Jersey localities, 

 however. The nymphs are very common beneath the floating 



debris and Spirogyra masses, and appears to be the most com- 

 mon species in the vicinity of Passaic except for an undeter- 

 mined species of Heptagenia from the brooks of this vicinity. 

 I have taken them at intervals from the first week in April 

 through July ; they were more abundant, however, during the 

 springtime. 



General color light brown, sometimes greenish ; eyes lateral; 

 body widest across the mesothorax ; legs about equidistant at 

 base, weak, light colored, darker at the tips of the joints. 



Gills exposed, on segments 1 to 7, simple, somewhat two- 

 lobed, broadly oval in outline, held vertically when at rest; 

 vibration intermittent but rapid (about 200 per minute). They 



