204 FAMILY V. — PENTATOMID^. 



Subfamily III. ACANTHOSOMIN^E Stal, 1864, 33. 



Pentatomids of medium or small size, having the thorax 

 armed beneath with a prominent central carina or keel which 

 extends the full length between all the coxae; abdomen also 

 with a prominent median carina, the sharp curved apex of 

 which extends forward between the hind coxae and overlaps 

 that of the sternum ; bucculae and beak as in subfamily Penta- 

 tominae; tarsi two jointed. 



This subfamily is placed by Van Duzee between the Penta- 

 tominae and Asopinae, but since the variation in the number 

 of tarsal joints is, in the Coleoptera, deemed of sufficient im- 

 portance to serve as the primary character in separating not 

 only families, but even series of families, it is, in my opinion, 

 of enough value here to warrant the isolation of those Penta- 

 tomids possessing only two tarsal joints and the placing of 

 them in a group following those which have three. The sub- 

 family comprises a dozen or more genera, mostly neotropical 

 in distribution. It is represented in North America and the 

 eastern states by only two of these. 



KEY TO EASTERN GENERA OF ACAXTHOSOMIN.E. 



a. Posterior side margins of pronotum depressed, their inner end 

 projected slightly backward opposite basal angle of scutellum; 

 outer hind angle of sixth ventral not strongly produced back- 

 ward; osteolar canal short, broad, curved, scarcely reaching middle 

 of its supporting plate; smaller, not over 9 mm. I. Meadorus. 

 aa. Posterior side margins of pronotum not depressed, their inner end 

 not projected backward; outer hind angle of sixth ventral acute, 

 strongly produced backward; osteolar canal straight reaching 

 much beyond middle of the metasternal plate; larger, 10 or more 

 mm. II. Elasmostethus. 



I. Meadorus Mulsant & Rey, 1866, 315. 



Small oblong-oval species having the head moderately de- 

 clivent, longer than wide, its apex rounded ; tylus slightly 

 longer than cheeks, its tip rounded ; beak slender, surpassing 

 hind coxae, its second and third joints subequal, fourth shorter; 

 pronotum with front portion strongly declivent, its side mar- 

 gins straight, entire, front angles with a small projecting 

 tooth, humeri obtusely angled, feebly concave or emarginate 

 behind the angle ; scutellum short, strongly tapering, the apical 

 third only half the width of corium, tip narrowly rounded ; 

 membrane surpassing abdomen, its veins simple; connexivum 



