Ch. 8: Mimicry and Warning Colours in Grasshoppers

There is in La Plata a large handsome grasshopper (Zoniopoda tarsata),
the habits of which in its larva and imago stages are in strange
contrast, like those in certain lepidoptera, in which the caterpillars
form societies and act in concert. The adult has a greenish protective
colouring, brown and green banded thighs, bright red hind wings, seen
only during flight. It is solitary and excessively shy in its habits,
living always in concealment among the dense foliage near the surface of
the ground. The yonng are intensely black, like grasshoppers cut out of
jet or ebony, and gregarious in habit, living in bands of forty or fifty
to three or four hundred; and so little shy, that they may sometimes be
taken up by handfuls before they begin to scatter in alarm. Their
gregarious habits and blackness--of all hues in nature the most obvious
to the sight--would alone be enough to make them the most conspicuous of
insects; but they have still other habits which appear as if specially
designed to bring them more prominently into notice. Thus, they all keep
so close together at all times as to have their bodies actually
touching, and when travelling, move so slowly that the laziest snail
might easily overtake and pass one of their bands, and even disappear
beyond their limited horizon in a very short time.

They often select an exposed weed to feed on, clustering together on its
summit above the surrounding verdure, an exceedingly conspicuous object
to every eye in the neighbourhood. They also frequently change their
feeding-ground; at such times they deliberately cross wide roads and
other open spaces, barren of grass, where, moving so slowly that they
scarcely seem to move at all, they look at a distance like a piece of
black velvet lying on the ground. Thus in every imaginable way they
expose themselves and invite attack; yet, in spite of it all, I have
never detected birds preying on them, and I have sometimes kept one of
these black societies under observation near my house for several days,
watching them at intervals, in places where the trees overhead were the
resort of Icterine and tyrant birds, Guira cuckoos, and other species,
all great hunters after grasshoppers. A young grasshopper is, moreover,
a morsel that seldom comes amiss to any bird, whether insect or seed
eater; and, as a rule, it is extremely shy, nimble, and inconspicuous.
It seems clear that, although the young Zoniopoda does not mimic in its
form any black protected insect, it nevertheless owes its safety to its
blackness, together with the habit it possesses of exposing itself in so
open and bold a manner. Blackness is so common in large protected
insects, as, for instance, in the un-palatable leaf-cutting ants,
scorpions, mygale spiders, wasps,