168 
[October 
question to decide with dried specimens gummed on paper. Finally 
it remains to be proved^ whether both are not identical with Ps. pedicu- 
larius, Linn.= Ps. domesticus Burm. They are certainly closely allied. 
Mr. Walsh has correctly remarked to me that on page 13 of my Synop¬ 
sis the pterostigma of Ps. salicis should be said to be “ posteriorly/’ or 
rather apically truncated, instead of “ anteriorly.” \_See note 3.] 
Ps. CORRUPTUS Hagen. The specimen sent me by Mr. Walsh seems 
in reality to belong to this species, but its wings are more deeply colored 
and the hyaline apical spot is subobsol^te, while it is very visible in the 
live individuals in my collection. Mr. Walsh writes me word that 
“Ps. corruptus is not the other sex of Ps. ahruptus’’ (as I have sug¬ 
gested in the Synopsis,) “ because the latter is very common, and the 
former very rare.” But this is well known to be the case in some 
European species. You may find thousands of 9 $ of hipunctatus 
together, and not a single S . It is the same thing with Ps. variegatus^ 
and especially, as it seems, with those species that live in some sort of 
society, while with the others, e. g., Ps. Imeatus.^ the two sexes are com¬ 
mon. I have seen 12 specimens of Ps. ahruptus all 9 , and 6 of 
Ps. corruptus all % . Finally, I have received in the same package and 
from the same places, (Washington, Dalton, Pennsylvania mountains,) 
the two species together. I agree with Mr. Walsh, (p. 362,) that the 
neuration of Ps. ahruptus may be reduced to the normal type of Psocus. 
but there are aberrations which I shall take occasion to explain at some 
future period, to justify the language used by me in the Synopsis. 
\^See note 4,] 
PERLINA. 
In this difiicult family my materials are now very rich, received from 
the Arctic and Subarctic regions and from Baron Osten Sacken, &c.; 
but they require a careful revision, which I hope to give them during 
the coming summer. For the present I may say that Acroneuria ru- 
pmsulensis Walsh is distinct from the Acr. ahnormis received from 
Mr. Walsh, and this last differs from the species referred by me to 
ahnormis.^ a specimen of which has been sent to me by Mr. Uhler as 
coming from Illinois. [See note 5.] The genus Pteronarcys requires 
an entire revision, and for that end I noted in London the form of the 
genital organs. Mr. Walsh is perfectly right in saying (p. 365) that 
