1863.] 
169 
the ‘‘postcostal space” is different and opposed to the “ postcubital 
space.” He views the subject exactly as I do. 
EPHEMERINA. 
Mr. Walsh’s method of breeding the Imago from the Subimago in 
this family, is the only correct way to arrive at a more perfect know¬ 
ledge of it, and I have endeavored myself to do the same thing here. 
But as in each species the S and 9 imago are often very different, 
and the S and 9 subimago different again, and as lastly living Ephe- 
merina are too different from the dried specimens to be able to deter¬ 
mine them from descriptions taken from dried specimens, we ought to 
have for each species eight descriptions ! Some considerable work 
yet to be done, before we can arrive at a correct knowledge of this 
family! 
B^tis. 
B. EEMORATA Walsh. I am not convinced that this is Say’s species. 
1,§^ The S ought to have “ the caudal setae hardly twice the length of 
the body,” or about 25 mill, (one inch), while the % subimago (Walsh) 
possesses setae only as long as the abdomen. Again, the 9 of Say’s 
species ought to have the setae nearly as long as the % . 2nd. Say 
says, “ thighs banded with reddish brown near the middle and at tip,” 
so there are two ha7ids, which are not met with in Mr. Walsh’s species. 
Srd. Says says, “ wings snowy white;” we cannot say that in B. femo- 
rata Walsh, the wings are of that color. 
In Mr. Walsh’s description it is said, “abdomen with joints 1—5 
whitishbut joint I is piceous, and it is 2 —6 which are whitish. He 
is right in remarking, that I erred in abridging Say’s language. After 
all, we may possibly agree with him, that the description of the legs is 
correct, for it corresponds with the legs of the S Imago; but it seems 
to me that the length of the setae is opposed to his opinion. This 
beautiful species is new to me. \_See note 6 .] 
B. ALTERNATA Say, (Walsh.) This species is new to me and is 
very probably the species of Say. The individuals mentioned by me 
(Syn. p. 49) are different—the venter fuscous, &c. 
Walsh Pseudoneur. p. 368 Baetis § A, and p. 370 Baetis §B, “First 
tarsal joint large always larger &c., is apparently an error, for “ lo7ig’^ 
and '‘doi^ger!’’ \^See note 7.] 
