EROTYLID^E 163 



While belonging to the affinis group, because of its pale head, pro- 

 notum and under surface, this species differs very much in having a 

 large testaceous spot at the base of each elytron, similar to that of 

 biguitata, and not extending to the humeral angles as it does in the 

 humeralis group. 



Triplax Hbst. 



The species of this genus have a facies quite different from that of 

 Tritoma, because of the more oblong and posteriorly obtuse form 

 of the body, and the antennae are longer and with a longer and looser 

 club; they are likewise found in fungi of various species and are 

 generally very abundant in individuals. The body is glabrous and 

 highly polished, but the pubescence on the abdomen is frequently 

 rather conspicuous. Festiva Lee., may be known at once by the 

 broad pale fascia of the elytra, but the latter in all the other species 

 are black or blue-black throughout, though paler basally in antica 

 and mormonalis. Of these, the only species having the under surface 

 entirely pale, described thus far from our fauna, is thoracica Say 

 (melanoptera Lac.) ; it is abundant to the eastward of the Appal- 

 achians, but in the Mississippi Valley there are several varietal 

 forms of it as follows: 



Triplax thoracica ssp. antennata nov. Similar to thoracica in coloration 

 and sculpture, but with the prothorax less, and the elytra more, abbrevi- 

 ated, the antennae a little longer, the third joint distinctly shorter as a 

 rule than the next two combined; head similarly large, much more than 

 half as wide as the prothorax. Length 3.44.8 mm.; width 1.7-2.3 mm. 

 Missouri (St. Louis) and Indiana. Very abundant. 



The corresponding dimensions of a good series of typical thoracica 

 from New York (Catskill Mts. and Lake Champlain). southeastern 

 Pennsylvania and one labeled Indiana, are 3.2-5.3 by 1.45-2.5 mm. 



Triplax thoracica ssp. obliqua nov. Stouter than antennata and with 

 shorter antennae, these in the female much shorter than the head and 

 prothorax, with joints 3-5 decreasing uniformly and very rapidly in 

 length, 5-7 a little longer than wide, the eighth as long as wide; head a 

 little smaller; prothorax of similar length, the sides parallel basally, 

 oblique and nearly straight in about apical half; scutellum shorter and 

 more transverse; elytra broader; abdomen rather more strongly punctate. 

 Length (9) 4-9 mm.; width 2.5 mm. Missouri (near St. Louis). 



Triplax thoracica ssp. brevicollis nov. Very small in size, the female 

 nearly as in the same sex of antennata, except that the head is relatively 

 wider, being nearly three-fourths as wide as the prothorax, the antennae 



