NO. 1571. DRAOONFLIES OF BURMA AND SIAM— WILLIAMSON. 



287 



angle of front wing free, of hind mng crossed. None of the species 

 has been taken in Burma or Siam. The two Indian species are very 

 similar and were regarded by De Selys as probably the sexes of a 

 single species. They are separated from, frulistorferi by having two 

 pale areas on either side of the thorax above, instead of one; by the 

 presence of a black stripe on second lateral suture, wanting in 

 frulistorferi; in aherrans and zallorensis there are 10-12 antenodals 

 in the front wing (7 or 8 in hind wing of aherrans), and 7-10 post- 



FlG. 13. -WlNfiS OF FEMALE DAVIDIUS FRUHSTORFERI FROM ToNKIN. 



nodals; in /m/;-.s'^or/^ri there are 14-lG antenodals in front wing, 10 

 in hind wing, and 11 or 12 postnodals in front wing and 10 in hind 

 wing. Characters for separating the two Indian species are not 

 evident in the descriptions. In both the abdomen is largely black, 

 1 and 2 largely 3'ellow, and the following segments to 8 each vnt\\ a 

 lateral basal and apical spot. The type of aherrans has the last 6 

 segments wanting. (See fig. 13.) 



Genus MACROGOMPHUS De Selys. 



The nine species belonging to this genus are confined to the Orient. 

 In addition to the two distinct patterns of thoracic colors, separating 

 these species into two grouj^s, venational differences exist, but 

 whether these venational differences are constant for the two groups 

 I do not know. I have seen only one species of each of the two 

 groups. In the case of the species of the quadratus group, in addition 

 to several minor differences, the greater complexity and remarkable 

 curving of the sectors, as compared mth the species belonging to the 

 farallelogrannma group, may be noticed. 



Quadratus group. — Dorsum of thorax black, with a large squarish 

 yellow spot on either side below. In quadratus De Selys, from 



