THE DRAQONFLIES OF SOUTH-WEST SURREY. 195 



portions of the wing,* and as an additional strength, helping the 

 Dragonfly to sustain its powerful flight. But this theory has 

 been considerably weakened owing to the fact that this thorn 

 structure is to be found on the wings of Agrionidce, Caloptery- 

 gidce, whose powers of flight are weak, and even the fragile 

 Ephemeridce. So for the present its use must remain a doubtful 

 question. 



Wishing to dissect the larva of a Libellula, to kill it I plunged 

 it into water at nearly boiling-point and left it immersed for 

 half a minute. When taken out, it recovered after a short time 

 and became as lively as ever. If the abdomen of a dead 

 Libellula larva be slightly pressed, the " mask " shoots out 

 automatically. 



* Cf. "The Adaptions of Aquatic Insects to their Environments," by 

 Gordon Dalgliesh. 'Journal of the Bombay Natural History Society,' 

 November 15th, 1909. 



