XVII] 



BIONOMICS, ETC. 



323 



yards. This distance was covered in three seconds ; so that this 

 Dragonfly can fly at the rate of nearly sixty miles per hour! 

 I doubt if any greater speed than this occurs amongst Odonata. 



Resting-Positions (fig. 166). 



The resting-positions of Dragonflies are well worth studying 

 and recording. Ability to escape from an enemy depends not 

 only on the speed of flight, but also on the method and quickness 

 of the "take-off from rest. Most Zygoptera choose their 

 resting-position for concealment. When danger threatens, they 

 are as likely to "orientate" themselves, by moving round the 



H 



Fig. 166. Typical resting positions of Dragonflies. A. Aeschninae. B, D. Libellu- 

 lidae. c. Gomphinae. E. Cordulephya. F. Diphlebia and Argiolestes. 

 o. Lestes. H. Agrionidae. Original. 



reed-stem to the side away from the approaching enemy, as they 

 are to fly off. Diphlebia and Argiolestes, however, resemble the 

 Gomphinae in their method of rest. They sit on rocks, sand or 

 twigs, with wings horizontally poised for flight. From such a 

 position they move off very rapidly. The Aeschninae alone, of 

 all the groups, regularly adopt a "hanging" position, which is 

 advantageous for concealment, but undoubtedly unsuited for 

 a quick take-off. In the Libellulinae, there is a similar habit of 

 rest, on the whole, to that of the Gomphinae, but with a tendency 



212 



