1G2 HYMENOPTERA. 



abflomen is pedicelled, and differs from Mimesa, a still more 

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

 less grooved, v»'hile in ]\Iimesa it is flat and not grooved at all. 

 Psen leucopiis Say has A dense silvery pile on the front of 

 the head, with black antennas, and the pedicel is rather short. 



NYSsoNiDiE Leach. In this famil}' the head is transversely 

 longer and less cnbical than in the preceding gronp ; the ver- 

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

 clypens long and narrow, the eyes long and narrow, and the 

 antennpe are more clavate than in the Crahroiiid«'^. ^nd 

 the pro[)odeum is sometimes armed with acute spines, while 

 the enclosed space is smoothly polished or striated. The wings 

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

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



In Trupoxylon 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 Odyuerus, 

 and into which it conve^-ed a small round ball, or pellet, con- 

 taining about lifty 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 Trypoxylon 

 had sulTlcient time to mortar up the orifice of the hole, and the 

 Odynerus was then entirely 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. politmn Say has purplish wings, and no enclosure on the 

 propodeum. 



T. frirjidum 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. 



Tiie genus MeUinus (belonging to the third subfamily, Mel- 

 liniua^^) is known by its broad front, and slender antenn:xi, 

 and its pedunculate abdomen, while in Ali/son, a slender- 

 bodied genus, it is sessile. MelUrnis hhuacidatus Say has a 

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

 spots on the abdomen. Alyson oppositus is black, with two 



