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



of the species, a fairly useful index for the determination of the species 

 will be found. 



Key to Species. 



A. Arc between the 1st and 2nd antenodal ner- 

 vures or opposite the 2nd. 



a. Abdomen of adult male not frosted with 



blue. 8th nervure from anal angle of 

 trigone, 

 i. Abdomen broad, depressed and tapering. 



Base of wings hyaline . . 

 ii. Abdomen relatively shorter and broader. 

 Base of wings golden yellow . . 



b. Abdomen of adult male but thinly frosted 



with blue, long, narrow and cylindrical. 



8th nervure separated from the anal angle 



of trigone . . 



e. Abdomen of adult male densely frosted with 



blue. 



i. Usually 2 rows of cells between 5 and 5fl. 



a'. Abdomen broad and depressed. 12 to 



16 antenodal nervures . . 

 b'. Abdomen narrow and tapering. 10 to 12 

 antenodal nervvires. Smallest species 



O. cancellatum. 



O. japonicum. 



O. trinacria. 



O. brunneum. 



angle 



of the genus 

 ii Only 1 row of cells between 5 and 5a. 

 d' Abdomen broad and depressed. Lamina 

 prominent, inclination to body-axis 45" 



to 60" . . 



b'. Abdomen narrow and parallel-sided. 

 Lamina depressed, inclination to body- 

 axis 30" 



B. Arc between the 1st and 2nd antenodal ner- 

 vures or occasionally opposite the 2nd. 



a. Abdomen densely frosted with blue. 



i 8th nervure widely separated from the 

 anal angle of trigone in the hindwing. 

 (Often only the first 3 segments of the 

 abdomen frosted with blue) 

 ii. 8th nervure arising from the anal 

 of trigone in the hindwing. 

 i'. Trigone in the hindwing traversed 

 ii'. Trigone in the hindwing entire . . 



b. Abdomen not frosted with blue, 

 i. Abdomen, dorso-ventrally, strongly 



at the anal end (segments 6-9). 

 8th nervure separated from the anal angle 

 of trigone in the hindwing 

 ii. Abdomen not dorso-ventrally dilated at 

 the anal end, broad and depressed. 

 8th nervure arising from the anal angle 

 of trigone in the hindwing. 

 i'. Adult male with a yellow or red forehead 

 a'. Male brilliant scarlet red. 



Wings relatively long and with a large 



basal spot in the hindwing. 

 No tuft of bristles on the lamina . . 



O. Ucniolatum. 



O. anceps. 



O. ransonnetti. 



O. chrijsostigma. 



O. trimKjularc. 

 O. fjlaucum. 



dilated 



0. sahina. 



O. testaeeum. 



