ii 4 ROD AND RIVER 



that, though the outer covering is rigid, the wing 

 enclosed in it, notwithstanding it is sometimes 

 more than twenty-four hours before the change 

 ensues, is kept moist and pliable. In proportion, 

 therefore, as the insect disengages itself from the 

 anterior part of the skin, the interior, or real 

 wings, become contracted by a number of plaits 

 into a form nearly cylindrical, which readily admits 

 of their being pulled through the opening lately 

 mentioned ; and as soon as the insect is released 

 from its envelope, the plaits unfold, and the wing 

 returns to its former shape and dimensions. 



' Thus one little animal, having bid adieu to its 

 shirt and drawers, becomes, but in a very harm- 

 less sense, a genuine descamisado and sansculotte. 

 It does not seem improbable that the pellicle we 

 have been speaking of is analogous to that which, 

 in addition to the outer skin, encloses the limbs of 

 Lepidoptera, etc., in the pupa state, but which they 

 cast at the same time with the puparium, and 

 leave adhering to it.' 



And again, in a preceding paragraph, where the 

 process of the expansion of the wings of flies 

 when emerging from the p'^pa, and the time taken 

 to perform the operation by them, is referred to, 

 he says : 



' In a few genera, however, as the gnat . . . 

 and the Ephemera, this process is so rapid and 

 instantaneous that the wings are scarcely dis- 



