TENTH LECTURE. 



ON THE DEVELOPMENT OF COLOR IN MOTHS 

 AND BUTTERFLIES. 



ALFRED GOLDSBOROUGH MAYER. 



IF one examines the wing enclosed within the wing-case of 

 a young lepidopterous pupa, it will be found to be transparent 

 and of a glassy clearness. A few days before the insect is des- 

 tined to emerge, however, the wings become pure white. This 

 white soon deepens into a dull yellow or ochre color, and then 

 the mature colors begin to make their appearance. They are 

 faint at first, but gradually deepen into the color of the mature 

 insect. They first appear in places near the center of the 

 wings, upon the interspaces between the nervures, not upon 

 the nervures themselves. Indeed, the nervures are the last 

 places to acquire the mature coloration. 



If we wish to comprehend the meaning of these color changes 

 which affect the pupal wing, we must first study the develop- 

 ment of the wing from its condition in the young larva up to 

 the time when the insect is about to emerge from the pupa. 

 In the caterpillar the future wings consist of small infolded 

 hypodermal pockets, which are situated upon the sides of the 

 second and third thoracic segments. The walls of these little 

 bag-like pockets are composed of closely crowded spindle-shaped 

 cells, and their inner cavities are penetrated by tracheae. When 

 the larva changes into a pupa, the wings expand to about sixty 

 times their former area, and, as a consequence, the cells which 

 compose the wing-bag, being no longer crowded, flatten out 



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