MEMBRACIDS MIMICKING ANTS 259 



prothoracic shield is modified into a resemblance to various 

 objects, such as seeds, thorns, &c. — an excellent example 

 of the parallelism between Mimetic and Protective Resem- 

 blance pointed out in Section 3, p. 225. The effects pro- 

 duced in the shield are at least as exact and detailed as 

 those which in other cases are wrought in the form of the 

 whole body. Thus, as Mr. W. F. H. Blandford has pointed 

 out to me, a peculiar characteristic of certain tropical 

 American ants (viz. the bead-like dilatation in the stalk 

 of the abdomen) is reproduced in the shield of the Mem- 

 bracid. This is well seen in Heteronotus trinodosus, shown 

 in Fig. 6, copied from Canon W. W. Fowler's Monograph 

 of the group in the Biologia Centi-ali- Americana. 



Finally, in the same group of Membracidae we meet 



FlG. 7. — About three times the natural size. On the right is represented an immature 

 Membracid {Rhynchota Bomoptera) from British Guiana, which resembles 

 an ant together with the leaf it is carrying. The latter is seen on the left, and 

 represents the species Atta {Oecodoma) cephalotes from the same locality. The 

 English leaf shown in the drawing is unlike the semi-circular fragments gnawed 

 by the ant. (From Poulton, Proc. Zool. Soc. Lond., 1891, pi. xxxvi, fig. 2.) 



with another example which is also incapable of inter- 

 pretation by any theory as yet brought forward except 

 Natural Selection. An immature form of Membracid, 

 with the prothoracic shield not yet formed, found by 

 W. L. Sclater in British Guiana, strongly resembles one 

 of the leaf-carrying ants which are so common in that 

 part of the world ; but the resemblance includes the leaf 

 as well as the ant ! The dorsal region of the Membracid 

 is flat and compressed, so that it is as thin as a leaf ; its 

 border (the dorsal surface, which forms a sharp edge) is 

 irregularly jagged as if gnawed, and during life it is green 

 in colour. Beneath this leaf-like expanse the brown head 



s 2 



