212 SEREICOENIA. 



12. Propleural triangle as wide at the base as, or wider than, the outer 



sj^e m Thambus. 



Propleural triangle at the base always notably shorter than the 

 outer side. 



Antennae with the third joint very small Diacerus. 



Antennae with the third joint longer than the second, and 



usually longer than the fourth Dromaolus. 



13. Antennal groove sharply limited internally by the margin of the 



triangle of the propleurse 14. 



Antennal groove not sharply limited internally, sometimes also 



punctate Plesiofornax. , 



14. Antennal joints 4-10 similar and of nearly equal length .... 15. 

 Antennal joints 4-7 very short, not longer than wide; outer joints 



abruptly much longer Dyscolotaxia. 



15. First joint of the hind tarsus distinctly shorter than the following 



joints together; antennal groove very broad; antennae ($) 



strongly pectinate Diphytaxis. 



First joint of the hind tarsus at least as long as the following 

 joints together; antennal groove never very wide; antennae at 

 most serrate. 



Prosternum normally convex in front of the coxae, the apex 



not elevated ; mouth-parts normal Fornax. 



Prosternum flat, slightly concave in front of the coxae, the 



apex abruptly elevated ; mouth-parts much modified . . Cladus. </ 



16. Margin of the prothorax with a single lateral ridge 17. 



Margin of the prothorax with at least two marginal carinae ; pro- 



pectus with a more or less defined juxta-sutural groove . . . 22. 



17. Mandibles with a broad rugose surface, the lower border more or 



less prolonged backward 18. 



Mandibles with a narrow surface, the lower border not prolonged ; 

 fourth tarsal joint simple 20. 



18. Last ventral segment not prolonged in an acute point ; antennae 



flattened, joints 2, 3, 4 equal in length Henecosoma. 



Last ventral segment acutely prolonged 19. 



19. Fourth tarsal joint excavate-emarginate. 



Metathoracic episterna parallel-sided Nematodes. 



Metathoracic episterna narrowed in front Trigonopleurus. 



Fourth tarsal joint slender and simple Emathion. 



20. Prosternal sutures straight; last three joints of the antennae 



abruptly longer * . Phlegon. 



Prosternal sutures arcuate ; antennal joints nearly equal . . . Anelastes. 



21. A distinct but not sharply limited marginal groove; last ventral 



segment abruptly prolonged in an obtuse point Diapodius. 



22. Propectus with a well-defined and limited juxta-sutural groove . 23. 

 Propectus without groove, with merely a slight and badly limited 



depression or smooth space 24. 



V 



