Biology of the Membra cidae of the Cayuga Lake Basin 327 



of the not mil. This position, which is not peculiar to the wings of the 

 Membracidae but is found in most of the famihes of the Homoptera, 

 causes a twisting and shifting of the parts of the wing base which requires 

 special attention. If the theoretical position as above described is con- 

 sidered the normal, the position of the membracid wing may be con- 

 ceived by imagining that the normal wing is first folded directly downward 

 and then bent backward until its long axis is parallel with the longitudinal 

 axis of the body. The movements necessary to accomplish such a change 

 in position are diagrammatically represented in Plate xxxiv, 5-7. It is 

 necessary to imagine that the horizontal plane representing the wing is 

 attached at some one point, for example a, about which it is free to move. 

 If then the distal end of the plane is moved downward until it is parallel 

 with the body wall, it will illustrate the first movement required. This 

 movement is not an unnatural one, since it represents a part of the normal 

 movement of the wing in flying. In order to reach the position desired, 

 however, the plane, still remaining flat against the body wall, must be 

 swung upward thru an arc of ninety degrees so that the long axis of the 

 plane is parallel to the long axis of the supporting wall. The plane is now 

 in the position assumed l^y the membracid wing. 



In order, however, to appreciate the mechanical changes that the wing 

 base has undergone, it is necessary to conceive of two points of attach- 

 ment instead of one, these points representing the anterior and posterior 

 angles of the articulating surface. It will be seen that the anterior point 

 will be pulled downward and backward, while the posterior point will be 

 moved upward and forward. 



This is apparently what has occurred in the wings of the Membracidae, 

 and it will be understood at once that such a migration of basal structures 

 renders difficult the homologizing of parts. In spite of the twisting, how- 

 ever, it is possible to reconcile to a large extent the shifted attachments 

 as shown in this family with the commoner interpretation of the wing base 

 in other insects. It has been noted, in the discussion of the pleural and 

 the tergal sclerites, that in the Membracidae no anterior notal wing 

 process could be determined, while the posterior process was prominent. 

 This is probably explained by the fact that the anterior angle of the 

 wing base has migrated away from its normal position, making the anterior 

 process unnecessary; while the posterior angle has moved upward, increas- 

 ing the musculature of the posterior region. 



