North American Hymenoptera. 291 



■¥ 



longitudinally each side, decidedly longer than the second 

 which is subemarginate above : abdomen oval, truncate, 

 subernarginate at base : jjleura striate like the head 

 behind. 



Length over three tenths of an inch. 



^ much more slender; transverse incisure between 



z 



the wings more obvious ; segments of the petiole not so 

 deeply divided. 



Leno^th over three twentieths of an inch. 



Neuter. Piceous varying to black ; abdomen cordate, 

 almost always black. 



Length under three twentieths of an inch. 



This species is very common in various parts of the 

 United States even in houses, and may be observed, by 

 every one, going in procession. The radial cellule is 

 slender and elongated, the including nervures being nearly 

 parallel ; the inner nervuredoes not quite attain the edge. 

 The first cubital cellule is hardly larger than the discoidal 



cellule, the recurrent nervure of which enters the first 

 cubital at the middle. Second cubital extendino: to the 

 tip of the wing. 



2. M. corrugata. Honey-yellow ; wings with three 

 complete cubital cellules. 



Inhabits Indiana. 



$ Body dark honey-yellow, almost piceous : antenna 

 whitish ; first joint not longer than the second and third 

 together; second joint rounded, thickest: metathorax 

 with two obtuse tubercles instead of spines : wings hya- 

 line ; nervures and stigma pale yellowish ; second cubital 

 cellule complete, nearly as long as the first cubital and 

 petlolated from the apicial angle of the discoidal cellule, 

 which is oblong subquadrate ; the descending nervure 

 from the stigma enters the second cubital : abdomen^ first 



