1898.] 



NATURAL SCIENCES OF PHILADELPHIA. 



145 



5. Orthetrum wrightii Selys. 



Lib'ellula wiigkHifkA.ja, Ann. Soc. Ent. Belg, xii, p. 96, 1869; Ann. Mag. 

 Nat. Hist. (4), iii, p. 272, 1869. O. W. Calvert, Trans. Amer. Ent. Soc, xix, 

 p. 163,1892; Proc. U.S. Nat. Mus., xviii, p. 134, fig. 12, 1896. Martin, 

 Mem. Zool. Soc, France, 1896, p. 102. 



Ten males, two females, Mahe Is., Seychelles. 



The pale spot on the upper surface of the frons, enclosed by blue- 

 black, is yellow in some individuals instead of olive. The front 

 wings with 12-14 antenodals, 9-10 postnodals, the internal triangle 

 4-celled in one male only. Inner side of the triangle of the hind 

 wings in the prolongation of the arculus in all. 



Having recently studied the type of 0. stemmale Burm. from 

 Mauritius, now in the Museum of Comparative Zoology at Cam- 

 bridge, Massachusetts, I have reached the conclusion that wrightii 

 is but a race thereof, as the only differences I can find are the 



following : 



Rhinariuru 



Black at the mid- 

 dle of the base 

 of the labrum 

 reaching 



Superior surfaces 

 of second and 

 and third fem- 

 ora and of first 

 and second tibise 



Inferior append- 

 age of the male 

 compared to the 

 superiors 



Total length 

 Abdomen (length) 

 Front wing (length) 

 Hind wing (length) 

 Pterostigma 



front wing 



hind wing 



stemmale, $ 



darker than nasus 



half-way to the 

 free margin 



luteous 



one-fifth 

 shorter 



50 mm. 

 34 mm. 

 36.5 mm. 

 34.5 mm. 



3.6 

 4. 



mm. 

 mm. 



wrightii, $ 9 



concolorous with nasus. 



to the free margin (except 

 in one young $ where 

 it reaches hardly half- 

 way.) 



black (or reddish-brown 

 in some immature 

 males.) 



one-fourth to one- third 

 shorter. 



46-39 $ , 44-41 9 

 31.5-27 ,£,31-28.5 9 

 34-29 $ 9 

 32-28 2 9 



3.4-3. $ 9 



