110 Ittinors NaturaAt History SurvEY BULLETIN 
Fig. 248.—Isonychia sayi, male genitalia. 
Fig. 249.—Isonychia diversa, male genitalia. 
Fig. 250.—Isonychia arida, male genitalia. 
Fore tibia entirely red-brown, sometimes 
shaded with darker brown at apex. .4 
4. Crossveins of disc of fore wing brown; 
penis lobes relatively short and narrow, 
GE ADI Dh tanare coe ne subs me 4. sicca 
Crossveins of disc of fore wing hyaline; 
penis lobes relatively longer and broad- 
CEES Ae 299 550 fase toe de tag tetes «atta 5 
5. Fore wing with stigmatic crossveins rela- 
tively numerous and anastomosed, 
1g” CO A aR ee a 5. rufa 
Fore wing with stigmatic crossveins rela- 
tively few, not anastomosed.......... 
iat eo ee aPinS Ee yee 6. bicolor 
1. Isonychia sayi new species 
Baetis arida? Say. Walsh (1862:370). 
Baetis arida Walsh, not Say. Hagen 
(1863:170); Walsh (1863: 191). 
Vol. 26, Art. 1 
BICOLOR 
Fig. 251—Isonychia rufa, male genitalia. 
Fig. 252.—Isonychia sicca, male genitalia. 
Fig. 253.—Isonychia bicolor, male genitalia. 
Siphlurus aridus Walsh, not Say. Eaton 
(1871: 129). 
Chirotonetes aridus Walsh, not Say. 
Eaton (1885: 206). 
Isonychia arida Walsh, not Say. McDunnough 
(1931¢:159) ; Traver (1935a:485). 
The name sayi is proposed for the species 
Walsh identified as Baetis arida Say. As is 
explained on page 111 below, Say’s species 
is another form, long unrecognized. I have 
seen some of Walsh’s original material, as 
well as McDunnough’s and Traver’s, and 
have found that the concept of arida Walsh, 
not Say, has not changed since Walsh’s 
time. 
Mate.—Length of body 9-12 mm., of 
fore wing 10-13 mm. Head light red-brown, 
