THE OPEN TYPE OF WING-GROWTH 97 



the fully-developed mayfly (or imago) ready for its brief life 

 of mating and egg-laying. No other insects besides mayflies 

 undergo a moult after having attained the power of flight, 

 and this feature, in conjunction with some of the larval pecu- 

 liarities just set forth, makes the life-history of mayflies of 

 surpassing interest to the student of insect transformations. 

 The importance of these features and their bearing on the 

 problems of insect life-histories will be better appreciated and 

 discussed after some examples of the hidden type of wing- 

 growth shall have been passed in review. 



