156 AGRIONS ; EPHEMERIDJE, OR DAY-FLIES. 



exist in this country ; the largest, which is surpassed in size by 

 few others, measures two inches and a half in length ; but the 



FIG. 472 A, the pupa with its mask. B, the same with the mask closed, and 

 discharging a current of water. j. 



foreign species are usually more brilliantly coloured. In the 

 Agrions, the wings stand perpendicularly when in repose, instead 

 of horizontally as in the Dragon-flies ; and the mouth is some- 

 what differently constructed. 

 The species represented in 

 the accompanying figure is 

 of a golden-green, or bluish- 

 green colour, with the wings 

 blue ; and, in common with 

 many other less conspicuous 

 species, it is an inhabitant 

 of Britain. 



738. The EPHEMERID^E, or Day-flies, receive their name 

 from the short duration of their lives in the perfect state. The 

 history of their early condition has been already given ( 690). 

 Their last change takes place near sunset on the fine days of 

 summer and autumn ; and they are sometimes produced in such 

 vast numbers at one time, that the ground is covered with them 



FIG. 473. AGRION VIRGO. 



