12G HYMENOPTERA OF AMERICA. [PART I. 



with the angles rather sharp. Metathorax quite rounded, offer- 

 ing two large dilated cheeks, strongly separated by a wide 

 channel; the lateral ridges effaced, rounded. Abdomen having 

 the same form as in M. coerulea, funnel-shaped, but its petiole 

 much shorter, forming hardly the third or the fourth of the first 



seg nt ; this retracts the second as in the Polistes, and carries 



a distinct groove above; the second segment having its border 

 insensibly subreflexed. Head and thorax very densely and 

 coarsely punctured throughout, of an elegant bluish-green violet, 

 having metallic reflections and garnished with a whitish pile, 

 especially distinct on the metathorax. Abdomen shining, black, 

 with some iridescent reflections; densely punctured, but with a 

 silky pile, of gray hairs. Legs black; the anterior tarsi at times 

 ferruginous. Wings brownish, with violet reflections; the ante- 

 rior edge darker. 



% . Clypeus polygonal, widely truncated, covered with a silvery 

 pile, offering toward the bottom two little arcuate carinae, which 

 end a1 the two distant teeth, limiting each side of the anterior 

 margin. The color of clypeus is bluish, like that of the head, but 

 it is marked on its anterior border with a double, pale, orange 

 spot ; the margin delicately black. Antennae black, rolled spi- 

 rally at the extremity, with the last article flattened, obtuse, and 

 ferruginous. .Mandibles almost without teeth, offering only some 

 feeble notches. 



Ress. ". diff. — This species approaches the 31. morosa, although 

 it i< easily distinguished from it by the blue, not black, color of 

 the thorax and the head its punctures are larger, not so dense; 

 the metathorax is more channelled and not so excavated; the 

 scutellum more flattened and parted in its length by a delicate 

 groove. The first abdominal segment is less dilated above ; its 

 base is linear, pedieulale for the length of a half line or less, 

 while with tie' 31. morosa this segment is more sessile. 



One mighl confound it also with 31. ccerulescens, of which it 

 lias much the appearance, except that its petiole is much shorter. 



JItih. The gulf side of Mexico. 1 have taken but one specimen 

 near Tampico. 



Observation. — This species is quite intermediate between Sect. 

 1st and Sect. 2d, its abdomen being rather pediculate. 



