J. C. HUTSON 211 



There is no apparent suture or line separating the mesopleuron 

 from the sternum or ventral plate. The latter is a large plate 

 occupying the ventral surface l^etween the fore and middle coxae, 

 and marked by a distinct median sutui'e with a shallow pit near 

 each end. About halfway between this suture and the upward 

 curve of the mesopleuron is a short line, sometimes appearing 

 distinctly incised with a shallow depression around it. 



The episternal groove is continued ventrally on each side and 

 curves forward to meet behind the bases of the procoxae. This 

 groove divides the mesosternum into the prepectus, or small 

 portion anterior to the episternal groove, and the mesosternum 

 proper, which extends to the bases of the mesocoxae, whose 

 articulations it bears. 



Metathorax. — The postscutellum is a narrow plate lying behind 

 the scutellum to which it is somewhat closely applied and in 

 front of the propodeum from which it is separated by a deep 

 fissure. Its lateral extensions are from two to three times as 

 broad as the middle portion, and have a deep cavity from which 

 the hind wings arise, and a nuich shallower cavity on each side 

 of the central portion of the plate. The posterior margins of 

 these lateral pieces are somewhat flanged and extend over the 

 anterior margin of the propodeum and the dorsal edges of the 

 metapleura. Outside the cavity of the hind wings on each side 

 is a small oval protuberance, sometimes called the metapleura! 

 lobe. 



The metapleuron is a somewhat indefinite plate, with its dorsal 

 portion lying oblicjuely under the hind wings and its ventral 

 extending horizontally under the side of the propodeum. It is 

 broad dorsally where its limits are well defined, but gradually 

 narrows ventrally when its boundaries become rather indefinite, 

 being more distinct in one species than the other. 



The hind legs are both at the ventral posterior end of the meta- 

 thorax, with the small metasternal area lying between the coxal 

 cavities. 



Abdomen 

 The median segment or propodeum lies between the post- 

 scutellum and the base of the petiole, and is bounded laterally by 

 the metapleura. It is really the first segment of the abdomen 



TRANS, AM. ENT. SOC, XLV. 



