One or two instances must here suffice.

In South America there is a family of butterflies, termed _Heliconidae_, which are very conspicuously coloured and slow in flight, and yet the individuals abound in prodigious numbers, and take no precautions to conceal themselves, even when at rest, during the night.

Mr.Bates (the author of the very interesting work "The Naturalist on the River Amazons," and the discoverer of "Mimicry") found that these conspicuous butterflies had a very strong and disagreeable odour; so much so that any one handling them and squeezing them, as a collector must do, has his fingers stained and so infected by the smell, as to require time and much trouble to remove it.
It is suggested that this unpleasant quality is the cause of the abundance of the Heliconidae; Mr.Bates and other observers reporting that they have never seen them attacked by the birds, reptiles, or insects which prey upon other lepidoptera.
Now it is a curious fact that very different South American butterflies{30} put on, as it were, the exact dress of these offensive beauties and mimic them even in their mode of flight.
In explaining the mode of action of this protecting resemblance Mr.Wallace observes:[25] "Tropical insectivorous birds very frequently sit on dead branches of a lofty tree, or on those which overhang forest paths, gazing intently around, and darting off at intervals to seize an insect at a considerable distance, with which they generally return to their station to devour.

If a bird began by capturing the slow-flying conspicuous Heliconidae, and found them always so disagreeable that it could not eat them, it would after a very few trials leave off catching them at all; and their whole appearance, form, colouring, and mode of flight is so peculiar, that there can be little doubt birds would soon learn to distinguish them at a long distance, and never waste any time in pursuit of them.

Under these circumstances, it is evident that any other butterfly of a group which birds were accustomed to devour, would be almost equally well protected by closely resembling a Heliconia externally, as if it acquired also the disagreeable odour; always supposing that there were only a few of them among a great number of Heliconias." "The approach in colour and form to the Heliconidae, however, would be at the first a positive, though perhaps a slight, advantage; for although at short distances this variety would be easily distinguished and devoured, yet at a longer distance it might be mistaken for one of the uneatable group, and so be passed by and gain another day's life, which might in many cases be sufficient for it to lay a quantity of eggs and leave a numerous progeny, many of which would inherit the peculiarity which had been the safeguard of their parent." [Illustration: LEAF BUTTERFLY IN FLIGHT AND REPOSE.
(_From Mr.Wallace's_ "_Malay Archipelago._")] As a complete example of mimicry Mr.Wallace refers to a common Indian butterfly.