DIPLAX. 177 



longly bifid ; wings hyaline, the extreme base yellowish; ptero- 

 stigma quadrangular, fuscous, terminated at each end with pale ; 

 membranule white; 7 8 antecubitals ; 7 8 postcubitals ; three 

 discoidal areolets. 



Length 32 37 millim. Alar expanse 50 58 rnillim. Ptero- 

 stigma 2 millim. 



Hob. Indiana; Massachusetts (Say); Maryland (Uhler) ; Bergen 

 Hill, New Jersey (Guex) ; Chicago ; Washington ; New York ; 

 Philadelphia (Osten Sacken). 



A common species. The variety described by Say 1. c. p. 27, 

 " wings with the basal half ferruginous" is unknown to me. 



I possess a male from Chicago most like this species, except that 

 the form of the hamules is different ; being shorter, the apex only 

 bifid, the external branch broad, truncated ; the internal branch 

 small, unguiculated : is it a distinct species ? 



7. D. albifrons f 



Libdlula albifrons Charp.! Libell. Europ. 14; tab. ix, fig. 3. Libellula 

 ambigua Selys, Revue Odonat. 325. 



Yellowish-subrufescent ; front narrow, yellow, no band before 

 the eyes; dorsum of the thorax luteo-fuscous, the sides paler, va- 

 ried with fuscous at the feet; feet luteous, the anterior femora ex- 

 teriorly, and the tarsi partly, fuscous ; abdomen long, slender, 

 sanguineous (adult male), or luteous ; segments 1 and 2 at base, 

 and segments 4 9 each side at the apex, with a triangular, black 

 spot; appendages luteo-rufons, superior ones of the male long, the 

 apex acute, recurved, beneath in the middle with a stout tooth ; 

 inferior appendage shorter, triangular, the apex a little excised ; 

 hamules long, the apex bifid, the external branch small, stout, 

 truncated; the internal branch longer, narrow, unguicnlated; gen- 

 ital lobe shorter, triangular; vulvar lamina broad, short, rounded, 

 the apex a little incised on the middle ; wings hyaline, extreme 

 base a little flavescent ; pterostigma quadrangular, fuscous, termi- 

 nated at each end with pale; membranule whitish-cinereous ; eight 

 antecubitals; 6 8 postcubitals; three discoidal areolets. 



Length 33 36 millim. Alar expanse 54 58 millim. Ptero- 

 stigma 2 millim. 



Hob. Georgia (Abbot); St. Louis (Engelmann). 



I possess the male described and figured by Charpentier ; the 

 locality as reported by him (" Switzerland") is erroneous. 

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