276 
MEANING OF SHAPES ANT) COLOURS OF THE MEMBRA Cl DHL 
the dark twigs of various trees from each other; for these also are reproduced upon 
the larvae. Thus Mr. Arthur Sidgwick has shown that the caterpillars, when found 
upon birch and oak, differ, as do the dark twigs of these two trees (l.c. p. 360). It 
has not yet been shown that any Membracid has this power of adjusting its colour 
to two or more environments, so that my argument does not at present apply to 
these insects. If, however, it is at all possible to breed them it would be deeply 
interesting to ascertain whether any such adaptability exists. The best chance of 
success would be afforded by experiments upon well-concealed species of which the 
individuals are known to vary greatly, but always in the direction of some one of 
their natural environments. 
It is now proposed to make a brief survey of the material illustrated in this 
monograph and to attempt to suggest the possible bionomic meaning of the appearances 
into which the enveloping pronotal shield is fashioned in the various groups of 
species. 
Commencing with the sub-family Membracince, the genus Membracis includes the 
species with the pronotum high and compressed from side to side, and coming to a 
sharp thin edge like a leaf. Beneath this leaf-shaped structure, which is dark, 
mottled with white or yellow, the head, wings, and legs of the insect are seen (see 
Plates I. and II.). Inhabiting the same part of the world, tropical America, in 
which alone this genus is found, are ants of the genus CEcodoma (Sauba ants). The 
ants live upon fungi which they cultivate in galleries underground, growing them 
upon a paste of bitten-up leaves. To provide this soil streams of ants are continually 
passing to the formicarium, each bearing a piece of leaf held vertically in its mandibles 
and thrown back over the body. The ants are extremely common, so much so 
indeed that certain kinds of imported trees cannot live in that part of the world, and 
the processions of leaf-carriers as well as the single ants are among the most familiar 
and characteristic of sights. The Membracidce on the other hand are scarce. Green 
leaves are not the only things sought out by the ants; they have been seen carrying 
off' parts of the wings of butterflies, as well as leaves discoloured in various ways. 
It seems possible that the rare Membracis with its high laminar pronotum may 
pass undetected among the numerous leaf-carrying ants which are partially concealed 
beneath their burdens in much the same manner. Furthermore the pronotum is 
about the same size as the fragment of leaf and the Membracid as some of the 
forms of the worker ants. 
I do not desire to press this interpretation with confidence, but merely bring it 
forward as a suggestion. 1 venture to hope that naturalists visiting tropical America 
will observe whether the leaves carried by the ants do not sometimes possess the 
curious parti-coloured appearance of the Membracid pronotum. 
