52 PROCEEDINGS OF THE NATION AI. MUSEUM. vou 63. 



20. PLATYGASTER ALNICOLA (Ashmead). 



Polymecus alnicola Ashmead, Bull. 45, U. S. Nat. Mua., 1893, p. 283. — Brues. 

 Bull. 22, Conn. Geol. Nat. Hist. Surv., 1916 (1917), p. 535. 



Female. — Length 2 mm. Head shaped as in pallipes Ashmead; 

 face not elevated in middle; occiput, vertex, most of cheeks, interocellar 

 area, and face around the ocelli strongly shagreened, much as in pallipes; 

 rest of face finely shagreened, without well marked transverse striae 

 above antennal sockets ; antennal process truncate anteriorly, the sides 

 only slightly ridged ; antennae moderately slender, the joints, except the 

 scape, combined about equal in length to the thorax; scape thick- 

 ened subapically, a little shorter than the five succeeding joints united^ 

 pedicel slightly over twice as long as wide, about as long as the two fol- 

 lowing joints united, a little wider than the fourth; third joint as 

 wide as long, narrowed basally, as wide as the fourth, half as long as 

 the fourth; fifth and sixth about as long as the fourth, a little thicker, 

 seventh nearly as long as and considerabl}^ thicker than the second ; 

 eighth and ninth distinctly but not much longer than wide, slightly 

 shorter than, but as wide as, the seventh ; tenth joint oblong-oval, as long 

 as the second, twice as long as wide; a little narrower than the ninth, 

 obtuse at tip; thorax twice as long as wide; pronotum shagreened on 

 the sides of the median area; notauli complete; median lobe of mes- 

 onotum rather strongly shagreened, the two lines on anterior third 

 narrow and depressed, not very distinct; lateral lobes shagreened 

 anteriorly along their inner margins, and along their outer margin to 

 apical half, othermse polished; scutellum transverse, highly convex, 

 margined laterally, shagreened and with a few short white hairs on the 

 sides; metapleurae, propodeum, first tergite laterally, and second ter. 

 gite at extreme base in the foveae, sparsely covered with short white 

 hair; abdomen a little longer than the head and thorax united-, as 

 wide as the thorax, shaped somewhat as in pallipes but shorter than 

 in that species; segments one and two united as long as the thorax; 

 median area on first tergite quadrate, the dorsolateral ridges sharp 

 and rather prominent; second tergite about as long as wide apically 

 somewhat narrowed basally, the sides feebly curved; basal foveae 

 broad and deep, covered with strong striae which radiate fan shaped 

 nearly two-thirds the length of the segment from the base; area 

 between the foveae with a few short striae laterally; third tergite 

 four times wider at base than long, three-fifths as long as the fourth 

 the sides oblique; fourth tergite twice as wide at base as long, the 

 sides oblique, straight, continuing the sides of the third; fifth as wide 

 at base as long, the sides not quite as oblique as those of the two 

 preceding segments; last segment as long as the fourth, one and 

 one-half times as long as wide, acutely pointed apically; front wings 

 extending to the apex of the fifth segment, hyaline, covered thickly 



