62 Trans. Acad. Sci. of St. Louis. 
Paederillus n. gen. 
This genus is much more boreal in range than Paederus 
and almost entirely replaces the latter in the United States, 
where it is distributed throughout from the Atlantic to the 
Pacific. Its species are much smaller as a rule than those of 
Paederus, and of more slender form, with little or no sexual 
difference in the head; the elytra are, however, frequently 
distinctly shorter in the male. The species are rather nu- 
merous but closely allied among themselves, having a remark- 
able persistency and uniformity of facies throughout. The 
coloration of the body is constant, being as stated in the table 
of genera, and the lustre is always shining, so that these 
characters will not be mentioned in describing the various 
forms below. The labrum is short and transversely truncate 
throughout and completely edentate, with a small abrupt sub- 
parabolic median sinus, devoid of medial denticle. The 
species are usually gregarious and therefore plentiful in in- 
dividuals when discovered; those represented by material in 
my cabinet may be described as follows : — 
Elytra large, much wider and longer then the prothorax in both sexes... 2 
Elytra shorter, never very much longer than the prothorax, even in the 
female, and occasionally much shorter except in texanus...-...+-.00. 8 
2— Body slender, the legs pale throughout, the antennae blackish, pale 
toward base and slightly paler at the immediate apex; head elongate- 
oval, the eyes rather small but convex and prominent and at one-half 
more than their own length from the base; sides behind them rapidly con- | 
verging, evenly, feebly and circularly rounded throughout to the neck, 
the angles obtuse and scarcely rounded, the base narrowly truncate; 
prothorax like the head subimpunctate as usual, elongate-oval, widest 
only slightly before the middle, narrower than the head; elytra very 
long, parallel, a third wider and more than a fourth longer than the 
prothorax in the male and distinctly wider than the head, the punc- 
tures only moderately coarse and unusually sparse; abdomen narrower 
than the elytra, parallel. Male with the fifth ventral very feebly sinuato- 
truncate at apex, the slit of the sixth narrow, parallel and very deep, 
the sides straight, the bottom of the slit concealed from view in speci- 
mens at hand; female not observed. Length 5.6 mm.; width 0.9 mm. 
WIGPid@s a\a5 base Mak hes cms de Leek ede Seow cies es eeee ses floridanus Aust. 
Body slender and nearly similar to the preceding throughout, except that the 
head is less elongate, the eyes a little larger, the sides behind them only 
feebly convergent and straight to the basal angles, which are rather 
