38 PKOCEEDINGS OF THE NATIONAL, MUSEUM vol.79 



There is so much variation in the color of this species from Illinois, 

 the type locality, that specimens from the Western United States 

 readily come within the extremes of the color differences. At first 

 inclined to look upon the western lots, as well as some from Illinois, 

 as representing several distinct species on account of both host and 

 color differences, I am at last compelled by the lack of structural 

 characters to regard them all as one. This same inconstancy of color 

 and absence of morphological characters make it impossible to 

 recognize varieties. These differences cut across the generic lines 

 of the cynipid hosts and do not correlate with any geographic boun- 

 dary, lines. 



13. DECATOMA DUBIA Walsh 



Plate 1, Figubb 12 



Decatoma varians var. duhia Walsh, Amer. Ent. and Bot., vol. 2, no. 10, p. 300, 

 1870. 



Readily separated from D. varians Walsh with which it has been 

 frequently confused, by its larger size, generally darker color, the 

 narrower and longer curved submarginal band, and the distinctly 

 relatively shorter and wider head which is much less produced in 

 front than in vanaiis. 



Female. — Length 3.2 to 4.3 mm., usually of the larger size, fairly 

 robust, mostly black above, some parts of body yellow to rufous and 

 brown; head black, except narrow circumocular band, temples and 

 cheeks mostly, malar space, antennal scrobe and an oblique bar from 

 it to eye, and face at times only below antennae and at times to and 

 including much of vertex, yellow or rufous-yellow, head almost 

 entirely black in a few Michigan specimens; scape light ochreous- 

 yellow, pedicel same but more or less fuscous above, ring joint yellow, 

 flagellum chestnut-brown ; sides of pronotum yellow like that of head, 

 top in most cases black, but at times only median third, or even only 

 posterior two-thirds of this area, black, rest yellow; mesothorax 

 black, lower parts of scapulae and axillae and the pleura deep yellow, 

 rufous, or brown to partly black ; metathorax and propodeum black ; 

 legs mostly yellow, front coxae immaculate to black on anterior 

 surface, middle and hind coxae sometimes rufous-yellow and sparsely 

 marked black, femora yellow, disks of outer surfaces sparsely and 

 feebly to broadly and deeply brown-black, tibiae light yellow, fore 

 tibiae at times immaculate, at times faintly brown, or front pair 

 faintly, and others increasingly brown, the hind pair deeply so 

 except base and apex, tarsi faint yellowish white; stigma almost 

 black, submarginal band deep dark brown, usually about two and a 

 half times as long as wide, its width almost uniform throughout, 

 rarely broader than length of stigma, crooked in form, bending 

 distinctly toward body, reaching two-thirds across wing, its apex 



