6. It is asserted that mimetic resemblances are produced in the most diverse ways; that the modes whereby the similarity in appearance is brought about are varied, but the result is uniform. “A lepidopterous insect,” writes Poulton (p. 251), “requires above all to gain transparent wings, and this, in the most striking cases that have been studied, is produced by the loose attachment of the scales, so that they easily and rapidly fall off and leave the wing bare except for a marginal line and along the veins (_Hemaris_, _Trochilium_).” 7. It is alleged that the imitator and imitated are always found in the same locality. If they did not do so no advantage would be derived from the resemblance. It is further alleged that where the mimicking species is edible it is invariably less abundant where it occurs than the species it imitates. 8. It is pointed out that it sometimes happens that where in the mimic the sexes differ in appearance, the male copies one species, the female quite a different one. This is said to be because the deception would be liable to be detected if the mimicking species became common relatively to that which is imitated. “We therefore find that two or more models are mimicked by the same species” (_Essays on Evolution_, p. 372). Occasionally the female mimics two other species, _i.e._ she occurs in two forms, each like a different species. It sometimes happens that the female alone mimics. This is said by Wallace to be due to her greater need of protection. When she is laden with eggs her flight is slow, and therefore she requires a special degree of protection. 9. It is said that in some species we find a non-mimetic ancestor preserved on islands where the struggle for existence is less severe, while on the adjacent continent mimicry has been developed. 10. It is alleged that in the cases where moths resemble butterflies the former are either as diurnal as the butterflies or are species which “readily fly by day when disturbed.” 11. It is asserted that some seasonally dimorphic forms are examples of mimicry only in one state, in the form that comes into being at the time when the struggle for existence is most severe; that is to say, in the dry season, in Africa, when insect life is far less abundant than in the rainy season. In other cases the mimicry of the dry-weather form is said to be far more perfect. Instances of this phenomenon are set forth in Professor Poulton’s _Essays on Evolution_. Alternative Theories It will be observed that we have quoted very largely from Professor Poulton’s work. Our reason for so doing is that he appears to be the most prominent advocate of the theory of protective mimicry, and his work, which was published in 1908, may be taken as the latest Neo-Darwinian pronouncement on the subject.