556 HYMENOPTERA. 



leaf, but that, in many cases, it was seated in the joint 

 itself, the whole substance of which became enlarged and 

 distorted. In a smaller number of cases, it was found to 

 occupy the culm or stem, above the joint, which was 

 swollen so as to form an irregular gall-like tumor, while 

 the leaf-sheath remained unaffected. These woody tumors 

 had several little cells in them, varying in number from 

 six to ten or more ; and every cell contained an insect, 

 in the pupa or chrysalis state. The samples of straw 

 reserved for myself were put into a small glass jar, to 

 secure the insects when they had completed their transfor- 

 mations. Early in May, winged insects began to perfo- 

 rate the tumors and come forth, and they continued to 

 issue during ten days or more. Their appearance was 

 probably hastened by the jar being kept in the house, in- 

 stead of being exposed to the air abroad. 



These insects so nearly resemble, in form, size, and color, 

 the Eurytoma formerly obtained from the barley-straw, that 

 I am persuaded they are at least mere varieties of the 

 same species, if not absolutely identical. The only ap- 

 parent difference between them consists in the color of the 

 fore shanks ; these, in the wheat-insects, being pale yellow, 

 and faintly tinged with black only on the outer edges, in 

 a few individuals. Among fifteen specimens only one male 

 was found, and this did not appear till the month of June. 

 Dr. Fitch obtained from his samples of straw above one 

 hundred specimens of the same kind of Eurytoma, and all 

 of them females. Among them he found another Chal- 

 cidian insect, a species of Pteromalus, probably a parasite 

 of the Eurytoma, and has favored me with a description 

 of it. The head and thorax are of a dark metallic green 

 color; the abdomen is slightly depressed, polished, purplish 

 black above, bright copper-colored beneath. The antennas 

 are black, except the basal joint, which is of a brilliant 

 copper-color. The thighs are pale yellow ; the shanks and 

 feet blackish, the hind pair with a broad pale ring around 



