176 NETJROPTERA OF NORTH AMERICA. 



Similar to D costifera, but the base of the abdomen is more in- 

 flated, the pterostigma shorter and broader, the anterior margin of 

 the wings clear hyaline. Is it distinct ? May it not be a variety? 



5. D. semicincta ! 



Libellula semicincta Say. Jour. Acad. Philad. VIII, 27, 15. 



Rufous ; front yellowish-red, with a broader black stripe before 

 the eyes ; dorsum of the thorax rufous, the sides inferiorly with 

 two obsolete, luteous spots, which are margined in part with black ; 

 feet black, the anterior femora luteous beneath ; abdomen short, 

 triquetral, the base a little inflated, rufo-fuscous, the lateral margin 

 and venter black ; the superior appendages rufous, cylindrical, the 

 apex black, before the apex beneath with a larger tooth ; the in- 

 ferior appendage hardly shorter, black, triangular, the apex a little 

 excised ; genital hamule short, bifid, the external branch stout, 

 conical, the internal one equal, unguiculated ; the genital lobe of 

 the length of the hamule, the apex rounded, broader ; wings hya- 

 line, fuscescent from the base to the nodus (not extending so far 

 upon the anterior wings) ; pterostigma quadrangular, fulvous, sur- 

 rounded with black nerves j membranule white. Male. 



Seven antecubitals ; six postcubitals ; three discoidal areolets. 



Length 30 millim. Alar expanse 46 millim. Pterostigma 2 

 millim. 



Hob. Indiana ; Massachusetts (Say) ; Pennsylvania ; Maryland 

 (Uhler). 



6. D. rubicundula ! 



Libellula rubicundula Say. Jour. Acad. Philad. VIII, 26, 14. Libellula 

 ambigua Ramb. Neuropt. 106, 105 ; Selys, Revue Odonat. 325. 



Yellowish-subrufescent; front yellowish, with a black band before 

 the eyes ; thorax rufous, the sides sometimes luteous ; feet black, 

 anterior femora luteous beneath; abdomen rather long, slender, 

 sanguineous (adult male), or yellowish rufous, the sides with a 

 maculose, black stripe ; appendages rufescent ; superior ones of 

 the male longer, the apex acute, recurved, beneath upon the mid- 

 dle with a stouter tooth; inferior appendage shorter, rufescent, 

 triangular, the apex a little excised ; the genital hamule rather long, 

 very bifid, the external branch triangular, the internal one a little 

 longer, narrow, subincurved; the genital lobe short, triangular, 

 the apex narrow ; vulvar lamina small, triangular, the base inflated, 



