150 AGRIONS ;< EPHEMERID^, OR DAY-FLIES. 



species of Dragon-flies exist in this country ; the largest, which 



is probably not surpassed in 

 size by any others, measures 

 two inches and a half in 

 length ; but the foreign 

 species are usually more 

 brilliantly coloured. In the 

 Agrions, the wings stand 

 perpendicularly when in 



FIG. 37'2. AGHION VIRGO. . . , 



repose, instead ot horizon- 

 tally as in the Dragon-flies ; and the mouth is somewhat dif- 

 ferently constructed. The species represented in the accompany- 

 ing 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. 



674. 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 ( 632). 



FIG. 373 EPHEMERA. 



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 

 after their death, and their bodies are carted away as manure. 

 They take no food after their final change ; and as the propaga- 

 tion of the race is then their only object, they die almost as soon 

 as it has been performed, often in a few hours after they have 

 quitted the water, the duration of their lives in their previous 

 conditions having been two or even three years. 



675. The TERMITID^, or White Ants, are terrestrial, active, 

 and carnivorous or omnivorous, during all their stages. In 



