(1) That the imitative species occur in the same area and occupy the very same station as the imitated. (2) That the imitators are always the more defenceless. {51} (3) That the imitators are always less numerous in individuals. (4) That the imitators differ from the bulk of their allies. (5) That the imitation, however minute, is _external_ and _visible_ only, never extending to internal characters or to such as do not affect the external appearance. In offering certain criticisms of the mimicry explanation it will be convenient to do so in connection with these five conditions which Wallace regarded as constant for all cases of mimetic resemblance. (1) _That the imitative species occur in the same area and occupy the very same station as the imitated._ This on the whole is generally true. It is well shewn in some of the most striking cases such as those of the Old-World Papilios that mimic Danaines, or of the Dismorphias and their Ithomiine models. In many of these cases the range of neither model nor mimic is a very wide one, yet the mimic is found strictly inside the area inhabited by the model. _Papilio agestor_, for instance, is only found where _Caduga tytia_ occurs, nor is _P. mendax_ known outside the area frequented by _Euploea rhadamanthus_. Even more striking in this respect are some of the Ithomiine-Dismorphia resemblances in the New World. The Ithomiine models are as a rule very local though very abundant. Two hundred miles away the predominant Ithomiine often bears quite a distinct pattern, and when this is the case the mimicking _Dismorphia_ is generally changed in the same sense. {52} But though mimic and model may be found together in the same locality, they do not always occupy the same station in the sense that they fly together. According to Seitz[25] the Dismorphias themselves do not fly with the Ithomiines which they mimic. The occurrence of butterflies is largely conditioned by the occurrence of the plants on which the larva feeds, and this is especially true of the female, which, as has already been noticed, is more commonly mimetic than the male. The female of _Papilio polytes_, for instance, is found flying where are to be found the wild citronaceous plants on which its larva feeds. On the other hand, its so-called models, _Papilio hector_ and _P. aristolochiae_, are generally in the proximity of the Aristolochias on which their larvae feed. The two plants are not always found together, so that one frequently comes across areas where _P. polytes_ is very abundant while the models are scarce or absent.