Mavfl, 



ics 



20 



The mayflies (order EbhemrrhhA o^ 11 

 They live in all U wafe^Sg ^ptdTSS 

 greatest diversity of situations 

 I he adults are fragile insects, hav- 

 ing long fore legs that are habit- 

 ually stretched far forward, and 

 two or three long tails that are 

 extended from the tip of the bodv 

 backward The wings are corru- 

 gated and fan like, but not folded 

 and are held vertically in repose.' 

 1 he hind wings are smalland incon- 

 spicuous. The antenna are minute 

 and setaceous. The head is con- 

 tracted below and the mouth parts 

 are rudimentary. Thus, many 

 characters serve to distinguish the 

 mayflies from other insects and 

 make their group one of the easiest 

 to recognize. 



Mayflies are peculiar also, in 

 their metamorphosis. They 

 undergo a moult after the assump- 

 tion of the adult form. Thev 

 transform tisually at the surface 

 ot the water, and, leaving the 

 cast-off nymphal skin floating flv 

 away to the trees. Body and wings 

 are then clothed in a thin pellicle 

 oi dull grayish and usually pilose 

 skm, which is retained during a 

 short period of quiescence. Durin°- 

 this period (which lasts but a few 



Fig. 112. An adult may- 

 fly, SipUonurus allern'a- 

 tus. 



one or two days) 



minutes in Can- an.; 4* allies, 

 b it wn. ninth arger .ns lasts 

 tht - ar. known as subimagrv: or 



