14 MISC. PUBLICATION 417, U. S. DEPT. OF AGRICULTURE, 
HYLASTES YUKONIS Fall 
Hylastes yukonis Fall, 1926, Pan-Pacific Ent. 2: 207-208. 
“Strikingly similar in size, form and general appearance to HZ. nigrinus, from 
which it seems to differ constantly in its somewhat less coarse sculpture both 
above and beneath. In nigrinus the punctures of the discal striae of the elytra 
are notably coarse, the intervals not appreciably wider than the striae. In 
the present species the strial punctures are evidently smaller, the intervals 
between the striae always distinctly wider than the punctures themselves. 
The sides of the prothorax are slightly more rounded than in nigrinus, and 
the rostral carina is always sharply defined and entire. In my series of nigrinus 
the rostral carina is never so well developed as in yukonis and not infrequently 
is nearly or quite obsolete except for the short distance where it crosses the 
apical convexity. Length, 43 to 5.6 mm.; width, 1.55 to 1.58 mm. Dimensions 
of type, 1.7 X 4.6 mm. ; of prothorax, 1.51.3 mm. ° 
“Described from six examples taken in flight at White Horse (June 21, 
1924), and Dawson (June 24, 1924), Yukon Territory. The type is a male from 
White Horse. 
“In the male the last ventral is apically concave and furnished with a brush 
of yellowish erect hairs as in the allied species. Notwithstanding the rugose 
sculpture the integuments of the upper surface are polished and shining through- 
out, without trace of alutaceous sculpture. Nigrinus is a little duller though 
not visibly alutaceous; the nearly allied macer, on the other hand, has the 
surface between the punctures distinctly alutaceous.” 
The present writer has seen no specimen of yukonis, but he has 
studied specimens of negrinus from several localities in Canada which 
approach it in structure. 
HYLASTES ASPER Swaine 
Hylastes asper Swaine, 1917-18, Canada Dept. Agr. Ent. Branch Bul. 14 (1): 
19-20; (2): TT. 
Female.—Very dark reddish brown, almost black, 4.55 mm. long, about 2.9 
times aS long as wide. 
Frons moderately narrow between eyes, frontal rectangle about 1.12 times 
as long as wide, dark reddish brown, with epistoma lighter reddish brown and 
its margin piceous; epistoma rather deeply, moderately broadly impressed at 
each side, median carina narrow and sharp below, wider above, ending at 
margin of central pit; epistomal margin piceous black, liplike; median lobe 
wide, rather short, broadly, deeply impressed in median line, with free end 
emarginate ; arcuate transverse impression rather weak, except in center, where 
it forms a subcircular pitlike depression as in nigrinus; surface moderately 
shining, very densely and finely granulate-punctate, vertex subopaque and very 
finely punctured; hairs fine, short, inconspicuous except on epistoma, where 
they are larger and directed orad. Eye finely granulate, about 2.3 times as 
long as wide, much wider above, inner line entire. Antenna with first segment 
of club distinctly longer than others combined. 
Pronotum distinctly narrower than elytra, about 1.14 times as long as wide, 
slightly wider near middle, posterior outline feebly arcuate, posterior angles 
searcely rounded, sides subparallel behind, feebly arcuate to widest point, then 
more Strongly, arcuately narrowed, very broadly rounded in front; surface 
shining, punctures moderate in size, very close on disk, granulate-punctate on 
sides, much smaller and denser, subgranulate in front; median line distinctly 
elevated, moderately narrow, hairs on disk minute, scarcely visible, somewhat 
longer but still short on sides and behind. 
Elytra distinctly wider than pronotum (54:44), about 1.9 times as long as 
wide, sides nearly straight and subparallel on anterior two-thirds, then grad- 
ually, arcuately narrowed to the moderately rounded apex; striae moderately 
narrow, moderately impressed on disk, more strongly so on declivity, less 
strongly so on sides; punctures rather small, closely placed, smaller on sides 
and declivity ; interspaces notably wider, moderately convex on disk, strongly 
