BATRISINI 217 



Key to Groups of Arthmius, Based on the Male Sex 

 (After Raflfray, 1904) 



Pronotum laterally flattened, and the disk medianly elevated into a 

 definite but obtuse longitudinal median carina or strongly longi- 

 tudinally gibbous 2 



Pronotum with sides and disk normally convex 3 



2. Fourth antennal segment distinctly larger than either the third or 



fifth segments, or antennae thick or otherwise abnormal I 



Antennae long, slender, simple II 



3. Antennae abnormal 4 



Antennae normal 5 



4. Legs abnormal Ill 



Legs normal IV 



5. Legs abnormal V 



Legs normal 6 



6. Dorsal surface of head abnormally excavated or armed 7 



Dorsal surface of head normal VIII 



7. Clypeus (epistome) normal VI 



Clypeus (epistome) abnormally excavated, tuberculated or otherwise 



armed VII 



Key to Species of Group I 



Six sternites fully visible (Males) 2 



Five sternites fully visible (Females) 4 



2. Distal margin of clypeus truncate, with rounded apical angle, and 



dorsal surface strongly elevated into a wide median longitudinal 

 biconcave carina ; antennal segment IV three times as long as third, 

 cylindrical but much wider than either third or fifth with the mesial 



face uniformly produced; 2.1 mm. long plicicollis 



Clypeus and antennae not as above 3 



3. Distal margin of clypeus medianly produced into a long horn with its 



subacuate apex tufted with setae; antennal segment IV ovate; 1.5 



mm. long barhiellinii 



Distal margin of clypeus strongly, evenly rounded and with the dorsal 

 surface tumid to end basally in a small pubescent horn; antennal 

 segment IV twice as long as third, with the mesial face strongly 



produced medianly, much wider than third or fifth ; 2 mm 



primariits 



4. Vertex with a strong median fossa; 2 mm. long crassicornis 



Vertex without a median fossa 5 



5. Known only from Mexico plicicollis 



Known only from Brazil 6 



6. North of Tropic of Capricorn barbiellinii 



South of Tropic of Capricorn primarius 



