114 PROCEEDINGS OF THE ACADEMY OF [Jan.^ 



nymphs were seen, while on September 11 both nymphs and adults 

 were taken at Garden Springs, and adults outnumbered the nymphs 

 at Marathon on September 12-13. From this it is apparent that 

 in the low, warmer Rio Grande Plain and interior valleys (Mesilla) 

 the species matures at least a month earlier than in the higher regions 

 of the plateau. The latest date is November 1-3 at Jaral, Coahuila. 

 Morphological Notes. — The subgenital plate of the male varies in 

 the depth of the emargination of the distal margin and also in the 

 degree of acuteness of the flanking angles of the same, in some exam- 

 ples these latter being quite acute and in others appreciably rounded. 

 The ovipositor varies slightly, almost inappreciably, in general 

 curvature of the margins and little in length, but the relative depth 

 varies very decidedly, particularly in all of the Mexican specimens,^ 

 which, however, are almost or quite equalled in this respect by 

 individuals of the sex from Kent and Garden Springs. The lateral 

 angles of the subgenital plate of the female vary in the degree of 

 angulation, in one extreme being practically rectangulate, in the 

 other with subspiniform extremities. While this latter variation 

 is frequently correlated with that in the depth of the ovipositor, the 

 rectangulate type with the deeper ovipositor, the more spiniform 

 type with the narrower ovipositor, this relationship is not at all 

 absolute. 



Synonymy. — By an unfortunate lapse, Scudder, when originally 

 describing this species, applied to it the same name (Dichopetala 

 hrevicauda) that he had given two years previously to a species now 

 known to belong to the genus Arethcea, as explained by Morse who 

 renamed the present form. The name brevihastata, proposed by 

 Morse to replace the preoccupied brevicauda, cannot, in our opinion, 

 be credited to Scudder, notwithstanding Morse's statement that the 

 name was suggested by him, as the note is entirely by Morse without 

 a direct quotation from Scudder. The naming of a species by proxy 

 does not seem possible under present-day rules. In the same paper 

 in which the last D. brevicauda was described, Scudder and Cockerell 

 recorded D. emarginaia from Mesilla Park on Airiplex, a locality and 

 situation from which they, a few lines below, described brevicauda. 

 There are no specimens in the Scudder Collection labelled emarginaia 

 from Mesilla Park or in the National Museum, and Prof. Cockerell 

 can give me no additional information. In view of these facts and 

 also that true emarginaia is not found within hundreds of miles of 

 that locality, as far as known only brevihastata occurring in that 

 region, it seems perfectly logical to assume that the determination 



