920 JOURNAL, BOMBAY NATURAL HIST. SOCIETY, Vol. XXVI. 



^li the forewing to hypertrigone rather more than a right angle, this trigone 

 narrow and traversed, in the hmdwing free (very occasionally traversed 

 in kirbyi). All hypertrigones entire ; subtrigone with 3 cells ; 1 cubital 

 nervure to all wings (kirbyi often has 2 in the hind wing) ; 4th nervure 

 variable, straight or undulated ; 2 rows of cells between 5 and .5«. ; dis- 

 coidal field with 3 rows of cells or rarely 1 or 2 rows of 4 ; more or 

 less contracted at the termeu ; anal field of hindwing broad and loop well 

 developed ; 4 or more rows of cells between the loop and the basal 

 margin of wing ; divided cells at the anal and external angles of the loop. 

 Membrane large. Stigma usually small and in one species bicolourous. 



Sexual organs : those of the male on the 2nd segment, large, the tenta- 

 cul^ variable and described under species ; lobe usually long, fairly 

 straight and narrow. Female : border of 8tli segment not dilated ; no 

 distinct vulvar scale ; 9th ventral plate keeled, furnished with 2 small 

 spines, the free border tongue-shaped and overlapping the 10th ventral 

 plate. 



'■^-Four species of this genus are found within Indian limits, two of which 

 are found throughout India and are probably about the commonest dragon- 

 flief} we have in this country ; the other two are local and one at least may 

 be considered scarce. A fifth species comes from Mesopotamia. 



Key to Species. 



1. Adult forms. 



A. Abdomen fusiform or clavate and depressed. 



Thorax and abdomen bright crimson, this 

 colour slightly violaceous due to a thin 

 pruinescence. 



i. Antenodal nervures 11^ to 15|^ .. T. aurora aurora. 



ii. Antenodal nervures 9^ to 10|^ . . T. annulata. 



B. Abdomen slim, cylindrical or triquetral. 



i. Thorax and abdomen bright vermilion 



red, with no frosting . . . . . . T. kirbyi kirbyi. 



ii. Thorax and abdomen black, this colour 



violaceous due to a thin pruinescence. T.festiva. 



iii. Thorax golden brown, abdomen black 



marked with yellow . . . . . . T. pallidinervis. 



11. Teneral forms. 



0, Abdomen very slightly fusiform or the sides 

 parallel and depressed, ochreous. 



i. Antenodal nervures 11^ to 16^ . . T. aurora aurora. 

 ii. Antenodal nervures 9f to 10^ . . T. annulata. 



57. Trithemis aurora aurora, Ris, 1911. 



Trithemis aurora, Brauer, 1868, Selys, 1882, Kirby, 1889, 1890, 



Karsch, 1891. 

 Trithemis soror, Brauer. 

 Trithemis adelpha, Selys. 

 Trithemis fraterna, Albarda. 

 Trithemis congener, Kirby. 

 Trithemis intermedia, Kirby. 

 Trithemis yerburyi, Selys. 

 Trithemis liturata, Selys. 

 Libellula aurora, Burm. 1839, Hagen, 1858, Calvert, 1898. 



