Pecftham — Revision, of the Attidce of North America. 361 
this difficult attitude the spider began to move. There was none 
of the awkwardness shown by Pellenes in trying to keep the third 
leg in position; indeed, there was no muscular action visible as 
he glided smoothly hack and forth, while the female, turning 
from side to side, kept him constantly in sight. The ready pen¬ 
cil of Mr. Emerton caught him in the act, and the figure speaks 
more effectively than words can do for the theory of sexual se¬ 
lection. 
E. monadnock, displaying ornamental fringe on first leg and color on third 
and fourth. 
Selection of any kind has no lack of material to work on 
among the Attidse, where variation may almost he called the 
rule, not the exception. In P. americana, for example, des¬ 
cribed by Keyserling, by Mr. Banks and by ourselves, nearly 
every example shows a new coloration for the hairs on the legs 
and palpi as well as of the falces, clypeus and crest; and of the 
male of oregonense, so common at Sisson in its delicate fawn 
colored garb which scarcely differs from that of the female, we 
have one example (from Oregon) with its entire body, cephalo- 
thorax, abdomen, clypeus, falces and legs clothed in bright iri¬ 
descent red. 
Several interesting phenomena remain unaccounted for. In 
the genus Pellenes are two closely related species the females of 
which are indistinguishable, borealis in the north and coronatus 
in the south. In borealis, when adult, the clypeus is black; in 
coronatus it is bright red. In the moults just before maturity 
the clypeus is bright red in borealis and dark in coronatus. 
One might hazard the conjecture that these spiders are the de- 
