VIII. A LIST OF THE DRAOONFLIES 



RECORDED FROM THE I N D I AN EMPIRE 



WITH SPECIAL REFERENCE TO 



THE COLLECTION OF THE 



INDIAN MUSEUM. 



Part II. {Contd). The Family Agrionidae. 



B. The Legions Argia and Agrion. 



By F. F. Laidlaw, M.A., M.R.C.S., L.R.C.P., 

 Lt., R.A.M.C. {temp.). 



(With text-figures 1-4.) 



Introduction. 



The first of these Legions is represented by a single species of 

 the genus Onychafgia, the only oriental genus which approximates 

 closely to the great American genus Argia, so prominent in almost 

 every part of the new world. 



The Legion Agrion includes genera which are commonly held 

 to be the most advanced of the Zygoptera. River species retain 

 few or no archaic characters ; are mostly of small or moderate 

 size ; are often very numerous in individuals^ and of wide distri- 

 bution. The Legion is in fact one of the dominant groups of exist- 

 ing Odonata, and its genera present a general similarity of struc- 

 ture, and especially of venation , which makes it a matter of 

 difficulty to arrive at a satisfactory natural classification ; exactl}^ 

 as the same difficulty arises in the case of other highly specialized 

 dominant groups, for example the Passeres amongst birds. The 

 table given below is an attempt to arrange these genera in such a 

 manner as to indicate their salient characters and as far as possible 

 to show relationships. It is a modification of the arrangement 

 suggested by Selys, his scheme being open to the objection that it 

 relies mainly on a sexual character. Tillyard's classification de- 

 pending as it does on a venational and purely adaptive character 

 has also grave disadvantages. 



Any clear-cut grouping is rendered all the more difficult by 

 the fact that one finds exceptional characters in certain species. 



In discussing venation I emplo}^ in this and other parts of 

 this list the modification of the Comstock-Needham nomenclature 

 given b3^ Tillyard, to be found in his book The Biology of Dragon- 

 flies. 



