INTERLOCKING MECHANISMS IN COLEOPTERA. 



297 



[d) Interlocking Mcclianisms found in Jliymalns. 

 Thymalus marginicollis is one of the trogositid beetles ; it has 

 the same general form as a lady beetle, but it is still better 

 adapted in form of body for clinging to a surface after the man- 

 ner of a limpet. The dorsal view of the body is a nearly perfect 

 broad oval showing simply the pronotum and elytra with a small 

 portion of the head. The flange on the edge of the elytron (seen 

 at /in Fig. 9) fits closely against the surface on which the beetle 

 is resting. The adult beetles are commonly found during the 



Fig. 9. 

 Xioo. 



Thymalus. Copied from Breed, -.ot,. Similar to Figs. S and 12. 



early part of the summer lurking about the shelf fungi which 

 have served their larvs as food. 



The four general methods of fastening the elytra in place which 

 were mentioned above are all functional in this beetle. The co- 

 adaptation between the body and the elytra is so perfect that it is 

 nearly impossible to unclasp the elytra in a dead specimen with- 

 out tearing them. 



