50 PROCEEDINGS OF THE NATIONAL, MUSEUM vol. 79 



darker extreme of dubia. The latter varies somewhat in length, 

 and even in the relative width and length of the head, the more 

 robust heads merging with the typical globuii head in dimensions. 

 In most instances, however, the head proportions, body length, and 

 number of setae on the submarginal vein readily distinguish them 

 and seem to justify their separation as two species. On the other 

 hand, small specimens of globuii grade into the larger Z>. nigriceps 

 Walsh in form of the head, size of body, and coloration. The 

 subglobose head and small size of the more extreme nigriceps require 

 that they be treated as distinct from glohuli. Here there seems to 

 occur a series of species merging into one another, without well- 

 defined specific limiting characters by which the border line indi- 

 viduals may be distinguished. All of them have at least certain 

 species of Disholcaspis as common hosts. 



18. DECATOMA NOVASCOTIAE, new species 



Plate 2, Figure 17 



Similar to dubia Walsh in being mostly black, and in having a 

 narrow, curved wing band, but is easily distinguished by its smaller 

 size, the lower numerical range of setae on the submarginal vein, 

 and in the distinctly narrower and longer, more blocky head. The 

 head of this species differs from that of most others of similar 

 dimensions in being almost equally long throughout its width. 



Female. — Length 2.6 to 3 mm., mostly black with some yellow, 

 brownish yellow, and brown ; head color quite variable, from mostly 

 black to mostly rich yellow, in one extreme only area around mouth- 

 parts and circumocular band, latter expanding caudad on temples, 

 yellow; in other extreme black on vertex continuing broadly over 

 occiput to neck, this briefly interrupted on occiput, and circum- 

 ocular band of yellow always present with varying width on vertex ; 

 face may be black to antennal fossae, and ocular band of yellow on 

 temples very variable in width, reaching occiput in a slender neck- 

 like band, or broadly, or expanding slightly and not reaching occi- 

 put; antennal scrobe yellow, scape mostly yellow, outwardly brown, 

 pedicel light brown, yellow at apex, flagellum almost uniformly 

 reddish brown or light brown; pronotum black above, occasionally 

 an oblique longitudinal fine stripe of yellow in middle of each half, 

 sides yellow full length but more broadly in front and extending 

 mesad along upper anterior edge, but not reaching middle; meso- 

 notum black, only scapulae sometimes feebly in front and behind, 

 and axillae on side in front, somewhat yellow, mesopleura yellowish 

 brown except upper portion of caudal half, which is black, meta- 

 thorax and propodenm black; coxae lemon yellow to dull yellow, 

 except front coxa, which is faintly fuscous outwardly, and outer 



