Among the butterflies we have numerous examples of the development from spots, as illustrated in plates. A good example is seen in our common English Brimstone (_Gonepteryx rhamni_) Fig. 2, Plate III. In this insect the male (figured) is of a uniform sulphur yellow, with a rich orange spot in the cell of each wing; the female is much paler in colour, and spotted similarly. In an allied continental species (_G. Cleopatra_) Fig. 1, Plate III., the female is like that of _rhamni_ only larger; but the male, instead of having an orange spot in the fore-wing, has nearly the whole of the wing suffused with orange, only the margins, and the lower wings showing the sulphur ground-tint like that of _rhamni_. Intermediate forms between these two species are known. In a case like this we can hardly resist the conclusion that the discoidal spot has spread over the fore-wing and become a blotch, and in some English varieties of _rhamni_ we actually find the spot drawn out into a streak. [Illustration: Plate III. BUTTERFLIES.] The family of _Pieridæ_, or whites, again afford us admirable examples of the development of spots. The prevailing colours are white, black and yellow: green _appears_ to occur in the Orange-tips (_Anthocaris_), but it is only the optical effect of a mixture of yellow and grey or black scales. The species are very variable, as a rule, and hence of importance to us; and there are many intermediate species on the continent and elsewhere which render the group a most interesting study. The wood white (_Leucophasia sinapis_) Fig. 1, Plate IV., is a pure white species with an almost square dusky tip to the fore-wings of the male. In the female this tip is very indistinct or wanting, Fig. 4, Plate IV. In the variety _Diniensis_, Fig. 2, Plate IV., this square tip appears as a round spot. The Orange-tips, of which we have only one species in Britain (_Anthocaris cardamines_) belongs to a closely allied genus, as does also the continental genus Zegris. The male Orange-tip (_A. cardamines_) is white with a dark grey or black tip, and a black discoidal spot. A patch of brilliant orange extends from the dark tip to just beyond the discoidal spots. In the female this is wanting, but the dark tip and spot are larger than in the male.