NORTH AMERICAN HYMENOPTERA. 91 



To this I liei'e add two uew species, both i-eared from species of 

 Lactuca or Mulgediiim (either L. Canadensis or M. leucophaeum I 

 cannot determine which witliout the leaves and flowers of the plants) 

 and both belonging to that section of the genus which Hartig has 

 designated as gall producers, "^'hey are all gall makers as distin- 

 guished from true Inquilines, but they do not, in all cases, produce 

 galls as the following descriptions will show : 



1. \. podagrte n. sp. 



The long, hollow stalks of Lactuca? Canadensis are often covered 

 in the upper half for a considerable distance with rounded swellings 

 of greater or less extent, that on being oi)eiied are found to contain 

 numerous Cynipidous larvte. The insects produced from these larvae 

 all have a closed radial area, and, without careful study, I placed 

 them among the inquilinous species, and went on rearing insects in 

 the hope of sometime finding the true gall-maker. 



I found that the larvte did not all live in the galls, but that the 

 pith of the stalks w^as full of larvae even where there were no indi- 

 cations of a gall. Sometimes the pith would contain larvae several 

 feet above and below the sfiace where galls were to be seen. 



The galls occur at the leaf nodes, where the ligneous walls of the 

 stalk are thickest, and it may be that the eggs laid between the nodes 

 are placed quite below the ligneous or fibrous part, and that the 

 j)oisou of the sting is inert in the purely cellular portion. 



I offer this as a conjecture only, having no j)roof that this is the 

 true explanation of a very curious fact. 



These insects evidently belong to the genus Aida.r, and, as above 

 remarked, to the gall-making division. 



The gall of A. podagrce is sufficiently described above, and the 

 desci'iption of the fly is as follows: 



Gall-flies. Female. — //earf black, vertex finely reticulated or punctate; an- 

 tennae dark brownish red, thirteen joints, first long and club-shaped, second one- 

 half as long, and the third only equal to the first in length, remaining equal and 

 slightly less in length than the third. Thorax black, mesonotum with a few- 

 scattered hairs and with minute, transverse lines or wrinkles, two lines reaching 

 half way to the scutellum, a median line, broad at its origin on the scutelluni, 

 but disappearing half way to the collare, parapsidal grooves entire, lines over the 

 base of the wings; all these very slender, but distinct, and shining; the collare 

 in this as in the species next described, very broad ; scutellum- rugose, fovese very 

 large and rugulose. Abdomen black, polished, second segment twice as long as 

 the third, and both forming nearly the entire abdomen ; feet the same color as 

 the antennae, deep brownish red. Wings hyaline, but showing, iu a favorable 

 light, a slight irridescence ; veins dark, and of nearly uniform size, areolet me- 

 dium size and well defined ; radial area broad, closed. Length : body. .10 inch. ; 

 wing.s, .10 inch. ; antenna^ .10 incli. 



