162 HYMENOPTEE A . 



iibdomGu is pedieelled, and ditiers from Mimesa^ a still more 

 slender-bodied genus, in having the tip of the abdomen more or 

 less grooved, while in Mimesa it is flat and not grooved at all. 

 Psen leucopus Say has a dense silvery pile on the front of 

 the head, with black antenna^, and the pedicel is rather short. 



Nyssonid^ Leach. In tliis family the head is transversely 

 longer and less cubical than in the preceding group ; the ver- 

 tex is liigher and more convex, while the front is narrow, the 

 clypeus long and narrow, the eyes long and narrow, and the 

 antennas are more clavate than in the Crabronidce, and 

 the propodeura is sometimes armed with acute spines, while 

 the enclosed space is smootiily i)olished or striated. The wings 

 are long and narrow, and the abdomen is sessile in the typical 

 genera, where it is obconie, but clavate when pedicellate. 



In Trijpnxiilon the body is long, with a pedicellate clavate 

 abdomen. In Europe "Mr. Johnson has detected it frequent- 

 ing the holes of a post pre-occupied by a species of Odynerus. 

 and into which it conveyed a small round ball, or pellet, con- 

 taining about fifty individuals of a species of Aphis ; this the 

 Odynerus, upon her return, invariably turned out, flying out 

 with it, held by her legs, to the distance of about a foot from 

 the aperture of her cell, where she hovered a moment, and then 

 let it fall ; and this was constantly the case till the Trypoxvlon 

 liad suflScient time to mortar up the orifice of the hole, and the 

 Odynerus was then entirel}- excluded ; for although she would 

 return to the spot repeatedly, she never endeavored to force 

 the entrance, but flew off to seek another hole elsewhere." 



T. politum Sa}^ has purplish wings, and no enclosure on the 

 propodeum. 



T. fi-ir/idum Smith lives in the stems of Syringa, from which 

 it has been reared by Mr. Angus. The thin, delicate cocoon is 

 long and slender, enlarging slightly towards the anterior end. 



The genus MeUinus (belonging to the third subfamily, 3Ie1- 

 h'nina',) is known by its broad front, and slender antennjv, 

 and its pedunculate abdomen, while in Alyson, a slender- 

 bodied genus, it is sessile. 3IelJim(s bivtaculatus Say has a 

 black head, with pale tipped antenuiv, and two ovate yellow 

 spots on the abdomen. Ahjson opjiositus is black, with two 



