80 NEOTROPICAL PSELAPHIDAE 



Tarsal claws euplectine, very unequal; a very large, rapidly very acute primary 

 claw, and an accessory bristle-like claw one-sixth as thick and less than half 

 as long as primary claw. 



Penis verj' large, bilaterally asymmetrical. Slide mount gives the length 

 as 0.126 mm., and 0.0504 mm. wide through the posterior muscular bulb. 



Female Allotype: As for the holotype with the following exceptions: 



Length 2.0 mm. x 0.85 mm. wide, that is shorter and broader. The eyes 

 are composed of 28 facets like the male, but the facets are very much smaller 

 so that the eyes are less prominent, and the tempora are twice the eye length. 

 Metasternum not medianly sulcate, but simply convex. 



First sternite not elevated as a prominent triangular platform between 

 the posterior coxae. First, third, and fourth stemites equal in length, fifth 

 sternite one-third shorter than fourth, sixth sternite one-fourth longer than 

 fourth or twice as long as fifth; second sternite the longest, 0.16 mm., two- 

 fifths longer than first or third. 



Tergites regularly decreasing in length, from first (0.26 mm.) to fifth 

 (0.1 mm.). 



Described on four specimens, all collected by Dr. E. C. Williams, Jr., 

 on Barro Colorado Island, Gatun Lake, Panama Canal Zone as follows: 

 Holotype male July 9, 1938 in floor mold sample No. 1342; Allotype female 

 July 29, 1938 in floor mold sample No. 345; Paratype male July 26, 1938 in 

 floor mold sample No. 285; Paratype male July 31, 1938 in floor mold sample 

 No. 1440. 



It is notable that both male and female have the anterior femora carinate. 

 The less prominent eyes and evenly convex metasternum serve to quickly dif- 

 ferentiate the female. Eurhexius zonalis is quite distinct from all others of the 

 genus on the described anatomy. The antennal differences between the two 

 sections of the fourth group are not so important as might be imagined, but 

 serve to differentiate certain groups from each other; on the other hand the 

 many structural differences are notable. 



Key to the Group V Species 



These three species make a definite approach to Aporhexius, but the pro- 

 notal margins are not simply crenulate, but instead have very minute, discrete 

 blunted denticules evenly spaced on the lateral pronotal margins. They are 

 quickly separable from the first four groups of the genus on the same char- 

 acter. It is possible that this group also includes Rhexius rugulosus Reitter. 



Size very large, in excess of four millimeters long; each lateral pronotal 

 margin with a minute tooth nearly opposite the transverse sulcus, 

 and five much smaller, blunted denticles evenly spaced between this 

 minute tooth and the apex; four elytral foveae arranged in two 



basal pairs muticus 



(Largest species of genus, 4.25 mm., and one of the 

 largest of the entire family; Bogota, Colombia) 



