_P. philenor_ is also regarded as serving as a model {47} for two Nymphaline butterflies in the United States. One of these is the large Fritillary _Argynnis diana_ of which the dark female has a markedly blue tint on the upper surface (Pl. XVI, fig. 3). The other is a _Limenitis_[23] related to our own White Admiral. This form, _L. astyanax_ (Pl. XVI, fig. 5), is a dark form with a bluish iridescence on the upper surface. It is found, like _P. philenor_, over the greater part of the Eastern States, while to the north, near the Canadian boundary, its place is taken by _L. arthemis_ with prominent white bar across both wings (Pl. XVI, fig. 4). There is reason for believing that where the two overlap there is occasional inbreeding, and that the hybrid is the form known as _proserpina_, resembling _astyanax_ more than _arthemis_. It must be admitted that in general appearance _L. astyanax_ and _Argynnis diana_ are more like _Papilio troilus_ than _P. philenor_. In explanation it has been suggested that all the mimics are on the way to resembling _P. philenor_, and consequently we should expect them at certain stages to shew more resemblance to one another than to the form they have all as it were set out to mimic. On this view they will all arrive at a close resemblance to _philenor_ in time. Another explanation is that favoured by Professor Poulton on which it is assumed that we are here dealing with a case of Müllerian Mimicry, all of the species in question being distasteful with the exception perhaps of _A. diana_. Thus _troilus_ and _astyanax_ though distasteful are less so than {48} _philenor_. Hence it is of advantage to them to have even a chance of being mistaken for the more obnoxious _philenor_, and so the one has come from the black and yellow Swallow-tail pattern and the other from the white-banded _arthemis_ form to what they are, _i.e._ more alike to one another than to _philenor_. They now form a Müllerian combination for mutual protection along with the dark females of _glaucus_ and _asterius_. But they are themselves still moderately distasteful so that it is to the advantage of the female of _Argynnis diana_ to mimic them. Whether they are all on the way to resembling _philenor_ more closely, or whether they have sufficiently vindicated their inedible properties and are now stationary, it is for the future to reveal to posterity. Lastly we have the view that these different species have attained their present coloration entirely independently of one another, and that we are not here concerned with mimicry at all. Since the sole evidence available at present is that based on general appearance and geographical distribution, the view taken of this case must rest largely upon personal inclination.