1865.] 363 



the following taken together; a short ovipositor protrudes iu a straight 

 direetiou from the tip; the radial area is closed on the anterior margin 

 by a somewhat paler vein, and the small second cubital is not opened 

 internally, but completely closed by a pale-colored prolongation of the 

 cubitus." 



It is not quite clear what Foerster means by the apex of the meta- 

 thorax, called, as he says, neck by Hartig. The last named author 

 called neck (cottum, compare the analytical table given above) what we 

 call the first abdominal segment, which is narrow, tubular, neck-like, 

 and sometimes (as in the genus Synergus) longitudinally striate. The 

 apex of the metathorax is quite a different thing ; it is a narrow pro- 

 jection of the metathorax. adapted, by its shape, to be iuserted in the 

 neck-like first abdominal segment. 



Having communicated to Dr. Reinhard specimens of N. A. Aulax 

 (A.sylvestn's), Synergus (S. lignicola and S. campanula) and Ceroptres 

 (two species) and having also obtained from him types of Aulax (four 

 species) and Synergus (three species), I have attempted to characterize 

 these genera in the sequel. The principal characters may be laid down 

 as follows : 



Synergus. —First abdominal segment longitudinally striate; the second oct 

 cupies, in both sexes, the whole remaining surface of the abdomen and conceals 

 all the following segments. 



Aulax. — Abdomen of a very different structure in the two sexes; in the male, 

 the second and third segments are subequal in length, and occupy, together, the 

 larger portion of the surface of the abdomen ; in the female, the second segmen- 

 alone occupies nearly the whole surface of the abdomen; first segment exceed- 

 ingly short, not longitudinally striate ; the third and the following more or 

 less concealed under the second. 



Ceroptres. — The second abdominal segment occupies, ira both sexes, the greater 

 portion of the surface of the abdomen ; a delicate, connate suture divides it appa- 

 rently into two segments. 



Among the unnamed species of my collection I possess one which 

 was communicated to me, in several male and female specimens, by Mr. 

 Bassett. He informed me that they were bred from stalks given to 

 him by some person, who said they were mustard stalks. Mr. Bassett 

 is of the opinion that by all means these stalks must belong to some 

 cruciferous plant. The pith of the stalk contains numerous round cells, 

 in which the insect probably underwent its transformation. 



The gall-fly has a closed radial area, the structure of which is nearer 

 to that of the gall-flies of the second section than to that of the first. 



