Casey — A Revision of the American Paederini. 191 
Lathrobium. The genera known to me by actual examples 
may be defined as follows: — 
Neck moderately narrow, varying from a fourth to nearly a third as wide as 
ChE OA. sv a'c cee dvdee vc beed cases che Ceca eapeletwad euogweea taeqgeccs 3B 
Neck extremely slender......cssecceccecccscccssscssscesscesesesecscess & 
2—Gular sutures parallel, broadly, feebly arcuate, moderately separated 
throughout but most approximate at the middle; labrum broadly trun- 
cate with the usual rounded median notch, bidentate or edentate; body 
parallel, moderately convex, always pale in color, the anterior thoracic 
angles distinct and subapical; tarsi moderately short, the posterior 
slender with the two basal joints subequal. Rocky Mountain regions. 
Leucorus 
Gular sutures more or less widely separated, more arcuate and most ap- 
proximate anteriorly, diverging thence gradually to the base; labrum 
distinctly quadridentate; hind tarsi short, moderately slender, with the 
basal joint but little longer than the second; body black or blackish, 
polished and more or less sparsely punctate....... eeeeeececcevsscen & 
3— Body thick and more convex, the legs thicker, the anterior tarsi di- 
lated; thoracic angles broadly rounded and almost obliterated, the 
prothorax oval; labrum truncate; gular sutures distinct. Entire United 
States except the true Pacific coast fauna. .........+++..++++ PyCnoras 
Body slender, moderately convex, the legs slender; anterior tarsi not dilated 
though broader and thickened; prothorax oblong, the anterior angles 
more or less distinct; labrum rounded; gular sutures very feeble, 
sometimes nearly obliterated. Entire Pacific coast region........QOrus 
4 — Posterior tarsi rather short, moderately thick, with the basal joint never 
more than slightly longer than the second, the anterior very feebly 
dilated; labrum rounded in outline, distinctly quadridentate, the teeth 
simple; body slender, parallel and moderately convex......ss.seseee 5 
Posterior tarsi long, very skender, with the basal joint always distinctly 
longer than the second, the anterior not or very feebly dilated; body 
subparallel, strongly convex, the prothorax oval with the anterior angles 
obtuse or subobliterated and far from the apex.......ssscccsecsesee 6 
5— Body minute in size, variable incolor, more or less alutaceous because 
of minute dense punctuation; prothorax suboblong, with the anterior 
angles more or less distinct; gular sutures moderately widely separated, 
most approximate anteriorly, gradually diverging thence to the base. 
Europe and America. [= Leptorus Csy.]...-..++++++ seeeseesSCOPACUS 
Body larger, black, polished, the punctuation less fine and rather sparse; 
prothorax oval, the anterior angles obliterated; gular sutures parallel, 
nearly straight, rather approximate throughout the length of the head. 
Entire northern United States....-+sseereeseeseceseeesess SCOPACOMA 
6 — Body very minutely punctulate and pubescent; labrum broadly rounded, 
large, very coarsely quadridentate and deeply cleft at the middle, the 
inner teeth each with an internal denticle at base, or, unequally bifid; 
gular sutures virtually coalescent from a short distance behind the sup- 
port of the mentum. Eastern United States..........¢. -- Scopaeopsis 
Body polished, subglabrous and subimpunctate, with sparse erect tactile 
setae; labrum broadly rounded, with the usual small median emargi- 
