MEANING OF SHAPES AND COLOVES OF THE MEMBRACIDjE. 7 



The larvje (Plate II. Fig. 4«) of the species of this genus are described by Canon 

 Fowler in the Biolofjia Centrnli- Americana as " very curious, being of much the same 

 shape as the perfect insect, but formed of separate upright narrow plates of different 

 heights." That these larvfe protectively mituic the leaf-carr3nng ants is highly 

 probable, far more so than in the case of the mature insects; for we have here the 

 testimony of a biologist who observed the living insect in its natural habitat. 

 Mr. W. L. Sclater, on returning from his journey to British Guiana in 188G, told me 

 that on one occasion while collecting insects by shaking the branches of a tree over a 

 sheet, his native servant, whom he described as a very acute observer, mistook one of 

 these Membracid larva? for a " Cooshie ant" carrying its fragment of leaf. 

 Mr. Sclater brought the larva home, and it is figured in a short paper communicated 

 to the Zoological Society {P.Z.S. 1891, p. 462, Plate XXXVL). In this case we 

 know that the thin flattened body is of a green colour like a leaf, while beneath it 

 the legs and head are brown like the part of the ant which is not concealed by 

 tlie leaf. 



It is of great interest that the remarkable forms of larva and perfect insect — 

 although superficially alike — are produced in entirely different ways. In the larva 

 the thin flattened shape is due to compression of the whole of the body rings behind 

 the head, and every one of them contributes to form the sliarp dorsal line which so 

 much resembles the serrated margin of a leaf or a jagged edge gnawed by the 

 mandibles of the ant. The same sharp line, forming a smoother sweep, is, in the 

 perfect insect, made up by the edge of the pronotum alone. If, therefore, both larva 

 and imago resemble leaf-carrying ants, the part representing the leaf is made up by 

 all the segments in the one, and by the pronotum alone in the other. Both larvae 

 and imagos probably live in the trees which the ants frequent for the purpose of 

 cutting the leaves. 



At first sight it seems very diflicult to account for the origin of such a case of 

 protective mimicry, if indeed the interpretation here suggested be correct. It 

 is, however, probable that the thin green body-form was gradually evolved to promote 

 concealment among leaves, and that the few special details which suggest the ant 

 were subsequently added. 



It is also of much interest that forms superficially resembling Memhracin 

 should be found in the Orthopterous genus XerojjliyUion (Plate I.) where thft dead- 

 leaf-like appearance is not confined to the pronotum but is further carried out in the 

 legs and head. The resemblance is clearly incidental and syncryptic. 



The appearance of the genera Pliyllofrojjis and Cryptonoius (Plates III. and IV.) 

 is not unlike that of Membracis. In the genera Encliophi/Jhim and Enchenopa (Plates 

 IV. to VI.) the pronotum is prolonged into a horn anteriorl}', in some species bent. 



