MEANING OF SHAPES AND COLOURS OF THE MEMBRACl DM. 275 
together : in the Membracidce the disguise is chiefly borne and often solely borne by 
the pronotum alone. The marked resemblance to ants in the genus Heteronotus, the 
strange and remarkable shapes which we should probably recognise as cryptic if we 
saw the living insects in their natural environment—these ai'e borne by a mask which 
is a development from a relatively small part of the organism. The Membracid, 
as a whole, bears not the slightest resemblance to ant or thorn or bark, but it is 
covered by a shield which does bear a striking resemblance in some species to the 
first, in others to the second, in others again to the third, of these objects. 
Those who oppose the interpretation based on natural selection are therefore faced 
by the question—how, except by selection, can it be conceived that the variations of 
shape in the pronotal shield of an insect can have been guided into the superficial 
resemblance to an ant, while variations in the whole body-form of another have 
assumed the same appearance, while in a third the likeness is indicated by colour 
alone, resulting in the invisibility of those parts which would interfere with the 
resemblance ? The attainment of the same end by entirely different means affords 
strong support to the opinion that the end is advantageous. On any other hypothesis 
as yet put forward it is a meaningless coincidence that the model suggested in each of 
these three different ways, is the same specially aggressive and well-known insect. 
This argument was first suggested by the present writer at the Toronto meeting of 
the British Association in 1897 (Report of the Meeting, page 692) and was further 
developed with the aid of illustrations in the Journal of the Linnean Society (Zoology, 
Vol. XXVI., pp. 588-595). 
In the following pages I have employed the word “ mimicry ” to indicate re¬ 
semblances to other species of animals. Likeness to plant structures, &c., for the 
purpose of concealment I have invariably called “cryptic” or “protective re¬ 
semblance.” Among the Membracidce such concealment is always “ procryptic,” for 
the purpose of defence; although anticryptic or aggressive resemblances to plants are 
well known in insects, especially in the flower- and leaf-like mantides (see page 153). 
In discussing the effect of hereditary bias towards particular colouring (see page 
200) I was considering only the cases of insects in which each individual possesses a 
power of special adjustment to two or more of its possible environments. For 
example the larva of the moth Amphidasis betvlaria have the power of becoming black 
on a plant with black twigs, green when the twigs are green, white when they are 
glaucous, &c. (Trans. Idnt. Soc. Lond., 1892, pp. 326-360). This individual adapta¬ 
bility and freedom from bias is clearly advantageous. If, for example, the effect of 
green shoots persisted in the next generation it would be injurious to the great 
majority of the larva, for the parent moth generally lays her eggs on plants with 
dark twigs. The same argument applies to the smaller differences which distinguish 
