60 Trans. Acad. Set. of St. Louis. 



Paederus Grav. 



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 about twice 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 grandis Aust. 



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 



