254 NEOTROPICAL PSELAPHIDAE 



Humeral callus simple, abruptly and bluntly terminated (PI. XVIII) 3 



3. Pronotum gibbous (by gibbous in this genus is meant a pronounced 



swelling of the pronotal disc, so that at least 50 per cent of the dorso- 

 ventral height of the pronotum proper is dorsal to a line drawn 

 through the basal and apical pronotal margins at their median 

 points; some species {globipennis) have the pronotum gibbosity 

 very pronounced, approaching the carinoid disc of Group I of 

 Arthmius and some Syrmocerus; other species {liljebladi and pana- 



mensis) have a simple gibbous condition as described) 4 



Pronotum not gibbous, the disc simply and evenly convex. . .Group IV 



4. Pronotum as long as wide or very slightly longer than wide . . Group II 

 Pronotum much longer than wide Group III 



In the following keys to species the male sex only is used. The majority 

 of species of Euphalepsus is known from this sex, few females having been 

 recorded. The secondary sex characteristics of females are correspondingly 

 poorly known. The female of centralis Sharp is described as having a conical 

 projection on the dorsal surface of the last tergite. The male secondary sex 

 characteristics are much better known, and in this sex the intermediate and 

 the posterior femora and tibiae are generally modified. A common pattern is a 

 spine or tooth on the ventral face of the intermediate femur and a spine or 

 tooth on the ventral face of the intermediate tibia, these spines varying specif- 

 ically in size, shape and exact position between closely related species. 



Partial Key to Group I 



Antennae with segments I to VIII inclusive forming one-half the total 

 antennal length, with IX, X, and XI forming a very elongate club, 

 these last three segments being very cylindrical ; head and pronotum 

 densely punctate, the punctures being subconfiuent; 2.24-2.44 mm. 

 pilicornis 



Antennae not as above 2 



2. Base of pronotum with three longitudinal carinae which extend from 



the basal margin to the transverse sulcus, one median and a sub- 

 median carina each side between the median carina and the lateral 



margin 3 



Base of pronotum not as described 4 



3. Antennal segments IX and X slightly transverse; 2.4 mm., .gounellei 

 Antennal segments IX and X elongate-oval, distinctly longer than 



wide ; 2 mm tricarinatus 



4. Here belong three Brazilian species, .bilineatus, bistriatus, longicornis 



Key to Group II, After Park (1933) 



Vertex strongly canaliculated ; a deep interantennal sulcus, commun- 

 icating laterally with a pair of anterior sulci which curve between 

 median frontal process and the antennal tubercle each side, and 



