XX 



INSECTA: NEUROPTERA 



303 



which lasts until the cold of winter renders further existence 

 impossible to it. 



Tennyson must have seen this 

 metamorphosis when he wrote : 



" To-day I saw the dragon-fly 

 Come from the wells where he did lie. 



' ' An inner impulse rent the veil 

 Of his old husk : from head to tail 

 Came out clear plates of sapphire mail. 



"He dried his wings: like gauze they 



grew ; 



Thro' crofts and pastures wet with dew 

 A living flash of light he flew." 



Other British Dragon-flies. 



Very nearly 2000 species of 

 Dragon -flies have been described, 

 and there are many more as yet 

 unnamed, but of all these only 

 about 46 are British. 



The four sub -families most 

 common in Britain are those the 

 typical genera of which are, 

 respectively, Libellula, Aeschna, 

 Agrion, and Calopteryx. Of these, 

 the two former are alike in being large forms with the 

 hind wings broad at the base, and in having larvae with 

 broad abdomen and anal respiration ; whilst in the two latter 

 all the wings are narrow at the base, the body has a very 

 slender long abdomen, and the larva also has a small slender 

 body with three flap-like processes at the end of it which are 

 tracheal gills. 



Sub-family 1 : Libellulidae. 



The imago of a Libellulid has a broad and thick though 

 tapering abdomen except in the genus Sympetrum. The com- 

 pressed eyes meet on the top of the head, and there are three 

 ocelli arranged in a triangle. The wings are extended when 

 at rest. The larva has a thick short body with slender weak 



FIG. 225. Last stage in the 

 metamorphosis of Aeschna, 

 the wings of the imago almost 

 fully expanded. 



