274 
evoluta for an Illinois species heretofore 
confused with arida as used in the sense 
of Frison 1935a. The transfer now of the 
name evoluta to my arida material of 
1935a leaves the species called evoluta in 
1937 “without a name,” as Ricker (1938) 
has earlier suggested. 
Part of the material listed by Needham 
& Claassen (1925) as arida belongs to the 
species | am now recognizing as arida 
(— valida) and part belongs to the spe- 
cies I am here recognizing as evoluta. 
Clark’s (1934) record of evoluta from 
Put-in-Bay, Ohio, mentioned as belonging 
to arida in my 1935a paper, again becomes 
part of the bibliography of evoluta as here 
recognized. Since Garman’s (1912) de- 
scription of “Larva No. 1” and his fig. 47 
are equivalent to arida in the sense of 
Frison 1935a, it also must be included in 
the bibliography of evoluta as now ac- 
cepted. 
Acroneuria prolonga Claassen (19376) 
was described on the basis of a single fe- 
male from “Bridger Mountains, Montana, 
June 19, 1914.” I have studied this type 
in the collection of Cornell University 
and consider it to be the same as my arida 
material of 1935a, which I am now calling 
evoluta as a result of Ricker’s remarks 
concerning the type. Any differences 
which might be observed between the sub- 
genital plates of evoluta, as now accepted, 
and prolonga are certainly slight and I 
believe well within the range of individual 
variation. 
For the convenience of other students 
and the bibliographic record, I have given 
the complete bibliography of evoluta to 
date. My only question is whether the 
name of evoluta is even now being cor- 
rectly used, a matter impossible to investi- 
gate further at this time. 
Acroneuria mela new species 
Acroneuria evoluta Needham & Claassen 
(L925 pal 8O) oma tele ast tepant. 
Acroneuria arida Claassen 
figs. 202 and 207). Nymph. 
Acroneuria sp. a Frison 
Nymphal description. 
Acroneuria evoluta Frison (1937, p. 79). 
Additional descriptive material and associa- 
tion of nymph. 
Acroneuria evoluta Claassen (1940, p. 173). 
Catalogue. 
(193 ten et 
(1935a, p. 405). 
As already mentioned in connection 
with evoluta Klapalek, it is necessary at 
Ittino1is NATURAL History SURVEY BULLETIN 
Vol. 22, Art 
this time to give a new specific name to 
the species illustrated and mentioned by 
me (1937) under the name of evoluta. In 
my article of 1937, I mentioned the possi- 
bility that my use of the name of evoluta 
for certain Illinois material, following its 
use “by Needham & Claassen (1925) for 
Fig. 40.— 
Acroneuria 
mela. 
ADULT HEAD 
AND PRONOTUM 
similar specimens from Kansas,’ was some- 
what dubious. Ricker (1938) has made a 
recent study of the typic female of evoluta 
in the collection of the Vienna Museum, 
and he states that it is not the same as the 
evoluta of Frison 1937 but “synonymous 
with arida Hagen [sense of Frison], as 
earlier suggested by Frison (1935:95).” 
When Ricker made his study of the type 
of evoluta he had available the published 
illustrations and descriptions  (Frison 
1935, 1937) to separate the two Illinois 
species at one time lumped as arida, but 
was not aware that the true arida 
(Hagen) = valida (Banks) was yet an- 
other species. his explains his statement 
of “synonymous with arida Hagen.” 
Claassen’s (1931) reference in his key 
to the nymph of arida, and his drawing 
(fig. 202) and photograph (fig. 227) of 
this nymph, should now be assigned to the 
bibliography of this new species since they 
are the same as my species a of 1935a and 
evoluta of 1937. 
Since this species has been confused in 
literature, and since, except for notes and 
illustrations in my stonefly paper of 1937, 
no single description certainly applies al- 
together to this species, I consider it ad- 
visable to treat it as a new species rather 
than to propose a new name as an append- 
age to previously mixed literature. 
Mave.—General habitus the same as 
for other species of Acroneuria from 
North America. Dorsum of head yellow 
with a pattern of dark brown markings: 
as in fig. 40. Pronotum with raised rugosi- 
