104 



[September, 1846. 



The committee on the following paper by Dr. Joseph 

 Leidy, reported in favor of publication. 



On the mechanism which closes the membranous wings of the genus 



Locusta. 

 By Joseph Leidy, M. D. 



The membranous wings or alee of the locusts while at rest are 

 folded up, like a closed fan, beneath the anterior pergamentaceous 

 wings. These are opened or expanded by the contraction of 

 appropriate muscles (extensores alse) contained within the thorax; 

 the tendons of which are inserted into the ribs or longitudinal 

 veins at the root of the wings. When one of the wings is sepa- 

 rated from the body of the insect, and stretched open by the 

 fingers, upon letting go, it will be found instantly to close or re- 

 sume the position of rest. 



The mechanism which produces this closure in the separated 

 wing, as well as when attached to the living animal, I find to 

 be spiral ligamentous bands, wound, like the thread of a screw, 

 around the transverse or connecting veins, which latter are also 

 flexible. By this arrangement, upon the contraction of the alary 

 extensors, the spring-like ligaments, or ligamenta spiralia as I 

 will call them, are stretched in the expansion of the wings, and 

 upon the relaxation or cessation of the action of the muscles, the 

 physical properties alone of the ligamenta spiralia, in resuming 

 their unstretched state, close the wings. These ligamenta spiralia 

 are numerous, and exist in all the species of Locusta possessing 

 perfect alas which I have examined. To this short description I 

 append a drawing of several of these ligaments, magnified, from a 

 preparation in Canada balsam, of one of the alse of Locusta Caro- 

 lina. 



