462 MR. E. B. pouLTON ON AN [June 1 6, 



8. On an interesting Example of Protective Mimicry dis- 

 covered by Mr. W. L. Sclater in British Guiana. By 

 Edward B. Poulton, M.A., E.E.S. 



[Received June 16, 1891.] 

 (Plate XXXVI.) 



An example of Protective Mimicry which I believe to be more 

 wonderful in its detail and complexity than any which has been 

 hitherto described, was observed and interpreted by my friend Mr. 

 W. L. Sclater in 1886 during his investigations in British Guiana. 

 Knowing that I was interested in the subject, Mr. Sclater kindly 

 communicated the observation to me and placed his material at my 

 disposal. I have already given a brief account of the example \ but 

 it seems of sufficient importance and interest to demand illustration ; 

 and I take the opportunity of saying a little more about it and of 

 answering criticisms. 



Mr. Sclater and his native servant had been collecting insects by 

 shaking the branches of a tree over a sheet. The servant, although 

 described as a very acute observer, saw an insect on the sheet which 

 he mistook for one of the abundant Cooshie Ants {(Ecodoma cephalotis) 

 carrying its little jagged segment of leaf over its back. Mr. Sclater 

 looked more closely and saw that it was an entirely different insect 

 belonging to the order Homoptera. The specimen has been sub- 

 mitted to Mr. C. Waterhouse, who states that it is an immature stage 

 of a species belonging to the family Membracid<E and probably to the 

 genus Stegaspis. 



Its length is 9 "3 mm., or ahout that of au ant carrying its leaf. 

 The leaf is represented by the thin flattened body of the insect, which 

 in its dorsal part is so compressed laterally that it is no thicker 

 than a leaf and terminates in a sharp jagged edge (Plate XXXVI. 

 figs. 1, 2). The head and legs were apparently brown, and sug- 

 gested the appearance of that part of an ant which is uncovered by 

 the piece of leaf. The jagged dorsal line when seen in profile 

 evidently corresponds to the roughly gnawed edge of the fragment 

 of leaf; for Mr. Sclater tells me that the contour of the latter is 

 generally shaped by the mandibles of the ant rather than due to the 

 natural margin, as represented in fig. 2. 



It is probable that the Homopterous insect invariably frequents 

 trees where too the ants would be well known and abundant. " The 

 example is, as far as I am aware, unique in the detail with which the 

 original is reproduced ; not only is the specially protected species 

 copied, but it is depicted at its usual occupation, and the material 

 upon which it labours is also included in the picture." '^ It is never- 

 theless possible to trace, with very probable correctness, the path 

 by which natural selection has produced so marvellous a result. 



1 ' Colours of Animals,' London, pp. 262-532. 

 ^ Ibid. p. 253. 



