Guiding BeeThe Evolution of Flight

Wing Folding

The wings are such crucial structures that without them, most adult insects cannot survive long or mate. One very important development in insects was the ability to fold the wings to protect them. The ancient order Odonata, which includes the dragonflies and damselflies, contains species of Carboniferous and Permian age with wingspans as great as one metre, the largest in insect history. Certainly, the ability to fold these wings would have been beneficial. The modern damselflies can fold their wings, but the dragonflies have not evolved the necessary musculature. Thus, dragonflies must rest with their wings fully spread and vulnerable. Beetles have hardened their front wings to form a protective cover, among other things, their hind wings. In addition to this, beetles fold up their hind wings under the shell like a letter stuffed into an envelope.

Below is a diagram showing how the stonefly Nemoura cinerea folds its wings. The process is analogous to the sorting of playing cards in the hand, only run in reverse. It is common in card games to receive a tight packet of cards (9 in the figure), open it out a little and sort the cards (8-6), quash the cards into a tight packet again (5-4), and fan them out in the hand, ready to play (3-1).

The Evolution of Flight...2, March 1996