THE LEG TENDONS OF INSECTS 



PKOFESSOR C. W. WOODWORTH 

 University of California 



While perhaps known to working morphologists, the 

 fact that the leg tendons are cuticular invaginations, and 

 therefore subject to replacement at each molt, does not 

 appear to have attracted the attention of any of the 

 writers of text-books, and as far as the writer of this 

 article is aware, has not been published at all. 



The three best developed tendons are the two operating 

 the knee joint and the one that flexes the claws. These 

 three are almost invariably present, though one or the 

 other may be very short, or present only as a cuticular 

 thickening. 



These structures are very easy to study in small insects. 

 I have found aphids the most satisfactory subjects. The 

 legs of most species are transparent enough to show the 

 structures well when mounted whole, and the exuvias are 

 especially satisfactory objects. They may also be ob- 

 tained in such abundance that one can mount large series 

 of specimens, thus obtaining mounts showing the legs 

 from almost any desired point of view. 



The knee joints provide for the largest amount of mo- 

 tion of any of the joints of the leg, and this motion is 

 all maintained in one plane by the development of two 

 bearing points, making a hinge. The end of the tibia is 

 small enough to telescope within the femur but for these 

 articular processes. They consist of a process project- 

 ing inwardly on either side of the rim of the femur, as 

 shown in Fig. 1, A and B, and corresponding with these 

 femoral processes there are slight outwardly projecting 

 processes from the margin of the thickened rim of the 

 tibia. The articular membrane at these points prevents 

 the displacement of the processes. 



