60 Trans. Acad. Sci. of St. Louis. 
Paederus Gray. 
The secondary sexual characters of the male are but 
slightly diversified, either in this or the other genera of the 
group, and are very nearly similar throughout, the fifth ven- 
tral being virtually unmodified, the sixth having a narrow par- 
allel-sided slit, two to four times as deep as wide. The slit 
sometimes has its edges beveled throughout as in grandis. 
The elytra of the male are nearly always perceptibly shorter 
than in the female and the head is sometimes much larger in 
that sex, but otherwise there is very little sexual difference in 
the facies. The anterior tarsi are strongly dilated in both 
sexes and clothed beneath with dense pads of short whitish 
spongiose pubescence. The various species are confined to 
the warmer parts of the United States, becoming very numer- 
ous in Mexico and are larger, as a rule, and heavier in build 
than those of Paederillus. The four in my cabinet may be 
known by the following characters : — 
Legs black, the femora pale in about basal half. Body large and rather 
stout, shining, the head and last two ventrals black, the elytra dark 
blue, prothorax rufous and abdomen flavo-testaceous; antennae black, 
pale toward base and apex; head in the male large, quadrate, wider 
than the elytra, with the basal angles very broadly rounded, the eyes 
only slightly prominent and at abouttwice their length from the base, 
smaller in the female, notably narrower than the elytra, with the sides 
converging and broadly arcuate behind the eyes to the neck; prothorax 
slightly longer than wide, strongly convex, ovoidal, perceptibly narrower 
than the head in the male but equal to the latter in the female, pol- 
ished, with a very few fine impressed and widely scattered nude 
punctures; elytra very coarsely and deeply but not densely punctate, 
quadrate, slightly wider than the prothorax and equal to it in length in 
the male, longer than wide, slightly longer than the prothorax and 
just visibly wider than the latter in the female; abdomen parallel, 
slightly narrower than the elytra. Length 9.2-10.5 mm.; width 
1.8-1.9 mm. Arizona..... sie 'en Ws Uhh RbNeb'seiah > cecie's sis sPRMGIS AUSE, 
Legs pale, the femora in rather less than outer half and the tibiae grad- 
ually, indefinitely and more nubilously toward base, black. Body 
otherwise nearly as in grandis, the head in the male large, quadrate, 
parallel at the sides, with the basal angles much less broadly rounded 
than in grandis; eyes nearly similar, the punctures moderately strong, 
few in number, widely scattered; prothorax only slightly longer than 
wide, strongly convex, not so greatly narrower than the head as in 
grandis, rounded at the sides anteriorly, scarcely punctured; elytra in 
