No. 39] ODONATA OF CONNECTICUT: LIBELLULIDAE 201 



Subfamily Cordulinae Selys 



The nymphs are closely allied to the Libellulinae, being sepa- 

 rable largely by the longer lateral and terminal appendages. 

 Some genera are more easily recognized by the presence of a 

 frontal horn on the head. 



The adults are also closely related to the Libellulinae, from 

 which they may be distinguished by tubercular or ear-shaped pro- 

 jections on the side of segment 2 of the male abdomen and the 

 small lobe on the caudal margins of the compound eyes. The lobe 

 of the compound eyes, however, is also present quite noticeably in 

 some of the Libellulinae and does not ofifer a clear-cut distinction 

 in all cases. The mesopleural suture (Fig. 40) does not have the 

 double curve of the Libellulinae, but even this character must be 

 used with care since there is some variation and not all species are 

 exactly similar to the figures. In the Cordulinae, in order to see 

 the suture, the surface hairs of the thorax must be scraped away. 

 The whole subfamily intergrades with the Libellulinae, and 

 persons not acquainted with the subfamilies often confuse them. 



For literature see: 

 Martin, Rene. Collections Zoologiques Edm. de Selys Longchamps, Fasc. 



XVII. 89 pages, 3 plates : 1906. 

 Needham, J. G. Annals of the Entomological Society of America, i : 273- 



280: 1908. 

 Williamson, E. B. Entomological News, 19: 428-434: 1908. 



Tribe Macromiini Tillyard 



The nymphs of this group may be separated from all others by 

 the presence of a prominent horn on the front of the head. The 

 adults are strong, active fliers, resembling Cordulegaster in color- 

 ation. The triangle of the hind wings is distad of the arculus. 



Key to Genera 



Nymphs 



1. Head hardly as wide across the eyes as across the hind angles ; 

 lateral spines of the ninth abdominal segment hardly surpassed 



by the tips of the terminal appendages (PI. rv, Fig. 5) 



Didymops, p. 202 

 Head widest across the eyes ; spines of the ninth abdominal seg- 

 ment not reaching the apices of the terminal appendages, usually 

 not longer than segment 10 Macromia, p. 204 



Adults 



I. Eyes contiguous but meeting in a single point only; margin of 

 hind wings between nodus and stigma more than half the length 



between stigma and the base of the wing (Fig. 41) 



Didymops, p. 202 

 Eyes distinctly contiguous, meeting in a mesal line of considerable 

 length ; margin of hind wings between nodus and stigma less 

 than half its length between base of the wing and the stigma 

 ( PI. XI, Fig. I ) Macromia, p. 204 



