FLIES FOR JUNE. 



107 



conviction that neither the dark nor light Green 

 Ephemera lay eggs (being imperfect insects), but 

 that their metamorphoses, the Grey Drake and 

 the Dark Mackerel, 1 lay eggs (whilst rising and 

 falling, &c.). This is an important fly on the 

 Blithe, and continues in season until the end of 

 June, and for part of July. 



1 The egg of this fly and that of all the last metamorphoses of 

 the Ephemeridse, here spoken of, sinks to the bottom of the water, 

 and is there, in a few days, hatched into a white grig ; this larva 

 undergoes several transmutations before it becomes a nympha, 

 which, rising to the surface at its appointed season, bursts the case 

 or skin which encloses it (at the shoulders), displays beautiful 

 wings, quits its old husk, and, after the lapse of a second or two, 

 generally flies to the nearest terra firma, where it remains in soli- 

 tude and shelter (from the wind and sunbeams) for about two 

 days (see fig. 22, plate 11). It then undergoes its last metamor- 

 phosis, and enters upon its imago or perfect state (see fig. 23), 

 changing the whole of its envelopes, even those of its fine tails and 

 legs. The tails and the two fore legs of the male increase to 

 about double their former length, those of the female receive an 

 accession of not quite one-third. The colour is generally altered, 

 the wings become shining and transparent. The male carries two 

 large stemmata upon his head, and a pair of callipers at the end of 

 his body, which two peculiarities chiefly distinguish his appearance 

 from the female. He is also usually rather smaller than she is. 

 He may be seen merrily dancing, as it were, up and down in the 

 air in vast crowds, frequently near a bush by the water side, 

 whilst the female is to be discovered busily employed rising and 

 falling and hovering over the water, and sometimes touching the 

 surface and making use of her long tails to spring up again. She 

 lays her eggs at this moment. 



The genus Potamanthus has three tails, or caudal setae ; Baetis 

 and Cloeon have only two of these appendages. 



