(2) yellow, (3) mixture of types, scarlet, yellow, orange, (4)yellow. Similar examples exist in the birds of the old world, but I do not know of any that have been studied so fully as those of America. The best known is that of the two Rollers, _Coracias indicus_ which spreads from Asia Minor through Persia, Baluchistan, the Indian Peninsula and Ceylon, and _affinis_ which ranges from Nepal, through Assam, Tenasserim and the Indo-Chinese countries. The two types are very different and may be distinguished as follows: _C. indicus_ _Mantle_ drab brown-chestnut. _Breast_ chestnut. _Throat_ purplish, streaked with white. _Upper tail-coverts_ indigo. _C. affinis_ Dark olive-green. Dull purple brown. Purple, streaked with blue. Turquoise. The wings are the same in both. In the provinces of Nepal, Sikhim, and Darjiling the two species coexist, with the result that intergrades have been frequently recorded. The line of intergradation extends to the coast, and birds showing various combinations of the two types from the Calcutta district exist in collections.[12] The case is interesting inasmuch as like that of _Quiscalus_ it shows a series of combinations of various metallic colours. Some of these are probably evoked by the development of pigment behind striations or other interferences already existing, but in the present state of knowledge it would be quite impossible to suggest what the actual factors producing these appearances may be. There are, naturally, many other cases among birds which are suspected of being in reality comparable, but in most of them the evidence is still inadequate. Among Lepidoptera also there are a few of these; perhaps the most striking is that of _Basilarchia "proserpina."_[13] The genus is well known to European collectors under the name _Limenitis_, of which we in England have one species, _L. sibylla_, the "White Admiral." A species very like _sibylla_ in general appearance is common in the northern parts of the United States, ranging through Canada and Northern New England, but rarely south of Boston. This species has the conspicuous white bands across both wings like our _sibylla_. There is also a more Southern type known as _astyanax_, which is very different in its appearance, being without the white bands and having a broad irroration of blue scales on the posterior border of the hind wings. The two are so distinct that one would not be tempted to suspect any very close relation between them. In its distribution _astyanax_ is described by Field as replacing arthemis south of latitude 42°. About Boston it is much more common than _arthemis_.