10 Myron Harmon Swenk 



illogical, and it seems best to consider Heminomada and Xan- 

 thidiuni as purely synonymous, and, as the older of these two 

 names is Heminomada, and in accordance with the law of priority 

 the oldest valid name must be used for the group, we must call the 

 subgenus Heminomada, even though for the bulk of the species 

 it is somewhat of a misnomer. 



The subgenus Heminomada, in this sense, differs from the 

 subgenus H olonomada chiefly in having the apex of the male 

 notched and antennal joint 3 almost always distinctly shorter 

 than 4, the apex of male Holonomada being entire and antennal 

 joint 3 of the female almost always longer than 4. The character 

 of the male apex seems to hold well, though some species plainly 

 referable to Heminomada (e. g., crazvfordi) have the notching 

 of the truncate termination of the apex exceedingly feeble in some 

 specimens; the proportion of the antennal joints is not quite so 

 reliable, however, and there are several species of Heminomada 

 (e. g., alpha) which have the third antennal joint as long as or 

 even slightly longer than the fourth, while on the other hand 

 some species of Holonomada {e. g., placida) may have the third 

 antennal joint a shade shorter than the fourth. On the whole, 

 however, the species seem to fall rather naturally into these two 

 groups, and it seems to the writer they merit recognition as 

 subgenera. 



The type species of Nomada (N. rnficornis) , as exemplified in 

 a pair from Alost, Belgium, determined by and received from J. 

 Bequaert, and agreeing with Schmiedeknecht's diagnosis of the 

 species, has simple coxae and mandibles, closely punctured vertex 

 and mesoscutum and no yellow ornaments on the thorax of the 

 female; antennal joint 3 is distinctly shorter than 4 and the basal 

 nervure is before the Iransverso-medial nervure, while the male 

 apex is notched. It is thus a member of Nomada sens. str. as 

 defined by Robertson. Nomada in this restricted or subgeneric 

 sense dift'ers from Holonomada in much the same characters as 

 does Heminomada, i. e., in having the male apex notched and 

 antennal joint 3 shorter than 4, and moreover we find here 

 species in which the notching of the male apex is exceedingly 

 slight (e. g., pallidipicta, beiilahensis), and other species in which 



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