It must be remembered that the two families are altogether distinct in structure.
The larvae of the Heliconidae are tubercled or spined, the pupae suspended head downwards, and the imago has imperfect forelegs in the male; while the larvae of the Pieridae are smooth, the pupae are suspended with a brace to keep the head erect, and the forefeet are fully developed in both sexes.

These differences are as large and as important as those between pigs and sheep, or between swallows and sparrows; while English entomologists will best understand the case by supposing that a species of Pieris in this country was coloured and shaped like a small tortoise-shell, while another species on the Continent was equally like a Camberwell beauty--so like in both cases as to be mistaken when on the wing, and the difference only to be detected by close examination.

As an example of the resemblance, woodcuts are given of one pair in which the colours are simple, being olive, yellow, and black, while the very distinct neuration of the wings and form of the head and body can be easily seen.
[Illustration: FIG.

23 .-- Methona psidii (Heliconidae).

Leptalis orise (Pieridae).] Besides these Pieridae, Mr.Bates found four true Papilios, seven Erycinidae, three Castnias (a genus of day-flying moths), and fourteen species of diurnal Bombycidae, all imitating some species of Heliconidae which inhabited the same district; and it is to be especially noted that none of these insects were so abundant as the Heliconidae they resembled, generally they were far less common, so that Mr.Bates estimated the proportion in some cases as not one to a thousand.