BRUES: PARASITIC HYMENOPTERA. 83 



EXETASTES INVETERATUS, Sp. nOV. (Fig. 63.) 



Female. Length 7 mm. Very dark colored, the abdomen except at the 

 base much lighter. Rather stout, the head thin antero-posteriorly. Antennae 

 long and slender, brown, the joints of the flagellum toward the base about 

 twice as long as wide. Mesonotum minutely punctulate; metathorax not 

 areolated, although there are some slight irregular indications of carinae. 

 Abdomen stout, contracted sharply at 

 the base, but not petiolate; first seg- 

 ment three-fourths as long as the sec- 

 ond; third and fourth together as long 

 as the second, fifth and sixth smaller. 

 Ovipositor two-thirds as long as the 

 abdomen, black. The abdomen is 

 smooth except the first segment which Fig. 63. — Exetastes inveteratus, sp. 

 is quite distinctly although delicately nov. Type, 



punctured. Wings hyaline; stigma 



and veins fuscous; areolet large, quadrangular, oblique, subsessile above; 

 marginal cell broad, sharply pointed apically, the second section of the radius 

 about two and one-half times as long as the first; stigma large, subtriangular; 

 discocubital vein sharply bent, but without trace of a stump of a vein; sub- 

 median cell considerably longer than the median. 



Type.— No. 2270, M. C. Z., Florissant, Col. (No. 7512, S. H. 

 Scudder Coll.). 



This species resembles in superficial appearance some of the species 

 of Mesochorus described in the present paper, but differs by the much 

 more sessile attachment of the abdomen and by the convex, non- 

 areolated metathorax. 



A considerable series of species occur at Florissant, seven in all, 

 which I have placed provisionally in the genus Mesochorus although 

 they are not very typical. In all of them the areolet is much smaller 

 than in recent forms, but otherwise they are quite similar. 



A very typical species of Mesochorus has been described by Scudder 

 ('90) from the Oligocene of Green River, Wyoming, but by him made 

 the type of a new genus, Lithotorus. Brischke ('86) also records the 

 probable presence of Mesochorus in Baltic Amber. 



Mesochorus Gravenhorst. 



Key to the Florissant species of Mesochorus. 



1. Areolet large, distinctly sessile above 2. 



Areolet petiolated or subpetiolated above; last section of the radius 

 not recurved (i. e. convex on side toward costal margin of wing). 



3. 



