no. 3601 TRIPLAX AND HAEMATOCHITON — JOHNSON 5 



the coxae are narrowly separated and the tibiae are weakly widened 

 apically. The hind trochanters are right triangular. The femora 

 are somewhat swollen. The tarsi are 5-segmented with segment 4 

 strongly reduced; segment 3 has all four sides straight or nearly so. 



One part of the male genitalia, the anterior end of the internal sac, 

 has been shown by Boyle (1956) to demonstrate specific diagnostic 

 relationships. The present study supports this. 



Little is known concerning the life habits of this genus. In eastern 

 North America favorite fungus hosts of Triplax species are species of 

 Pleurotus, a soft bracket fungus; and in Arizona, T. ihompsoni has been 

 taken in large numbers on Polyporus arcularius on oak. 



Genus Triplax Herbst 



Triplax Herbst, 1793, p. 146, pi. 49 (figs. 13, n). [Type-species: Silpha russica 

 Linne, 1758, p. 360, by subsequent designation by Curtis, 1838 (1824-1840), 

 vol. 15, p. 706.] 



The following key to the Neotropical members of the genus Triplax 

 includes three species — T. thompsoni, T. marcescens, and T. cali- 

 jornica — the Mexican specimens of which are not definitely known. 

 It is believed, however, that their ranges extend into Mexico, and for 

 this reason they are included. 



Key to Neotropical Species of Triplax 



1. Antennae black beyond segment 2, the stem clothed with moderately dense, 



coarse, black setae; antennal club narrow, segment 10 no more than 

 twice as wide as segment 7; head above entirely reddish yellow; Arizona, 



Mexico? marcescens Boyle 



Antennae not black or not entirely black, at least part of the antennae in 

 addition to segments 1 and 2 lighter 2 



2. Elytra distinctly margined basally 3 



Elytra immarginate basally, at most with a vestige of a margin laterally 



near the humeral callus 10 



3. Pronotum bearing a median apical and a smaller piceous spot near the 



middle of each side, the latter often weak, sometimes obsolete; anterior 

 and lateral edges of postmandibular lobes sharply rounded, not posteriorly 



divergent; southwestern U.S., Mexico mesosternalis Schaeffer 



Pronotum without spots 4 



4. Elytra yellow to red 5 



Elytra never entirely yellow to red, some portion or all piceous to black . . 6 



5. Pronotum piceous to black, not yellow to red; Texas, Mexico . errans Boyle 

 Pronotum yellow to red; Central America .... alvarengai, new species 



6. No part of pronotum black ... 7 



Some part of pronotum black 9 



7. Abdomen usually testaceous; terminal segments of maxillary palpi moder- 



ately widened, their width less than 3 times length; eastern North America 



to Panama flavicollis Lacordaire 



Abdomen not testaceous; terminal segments of maxillary palpi strongly 

 widened, their width more than 3 times length 8 



