BAETIS. 49 



wings snowy hyaline, veins clouded with fuscous, especially the 

 basal, discoidal and apical ones. 



9 Fuscous, thorax yellowish, venter whitish ; feet pale fus- 

 cous, a reddish-brown band upon the middle and apex ; seta? nearly 

 the same length as with the male ; wings whitish, veins fuscous, 

 clouded with fuscous. (From Say's description.) 



Length of body 12 millim. Setae 24 millim. 



Jfab. Cincinnati, Ohio (Say). Not common. Similar to the 

 preceding species; it may be the same or B. annulata. 



15. B. alternata ! 



Baetis alternata Say, Long's Expedition II. 304, 2. 



Fuscous ; head in front and at sides whitish ; thorax pale fus- 

 cous, in front yellowish, sides varied with yellow; feet pale ochra- 

 ceous, an apical fuscous ring upon the femora; abdomen above 

 fuscous, segments at base whitish, the two last with two whitish 

 lines; venter whitish, each segment with two oblique lines and two 

 intermediate points black; setas whitish, regularly pointed with 

 fuscous; wings hyaline, veins not margined. (From Say's descrip- 

 tion.) 



Length of body 12 millim. 



ffab. Northwest Territory (Say). 



I would believe that a male imago and subimago and a female 

 subimago from Maryland, communicated by Mr. Uhler, belong 

 here, but the femora have a medial and apical band. 



The < subimago is paler ; wings gray, opaque, veins a little 

 clouded with fuscous. 9 subimago obscurer, feet uniform fus- 

 cous ; wings blackish-fuscous, posterior ones yellowish at base, 

 veins not clouded. 



Length of body 12 millim. Alar expanse 30 millim. Seta3 g 

 27, millim. Male and female, subiraago, setae 15 millim. 



I saw subimagines like the female, from Washington (Osten 

 Sacken). 



16. B. luridipennis. 



Baetis luridipennis Burm. II, 801, 7. Pict. Ephem. 192. Walker CataL 

 563, 27. 



Fuscous ; abdomen banded ; wings lurid, veined with fuscous 

 (Burm.) J and subimago fulvous; antenna? fuscous; margins 

 of the abdominal segments fuscous ; setffi whitish., covered with. 

 4 



