The monkey ate various forms of Precis (a Vanessid), after which it was given Acraea halali. This distasteful form was "accepted without suspicion, but when
the monkey put it into his mouth, he at once took it out again and looked at it with the utmost surprise for some seconds, and then threw it away. He would have nothing to do with an Acraea caldarena which I then offered him[[78]]."
The experiments with the baboons were more extensive. Two species of Acraea, halali and axina, were recognised when first offered and refused untasted. Danais chrysippus, on the other hand, was tasted on being offered for the first time, and then rejected. This species was twice offered subsequently and tasted each time before being rejected. When offered the fourth time it was rejected at sight. The baboon evidently learned to associate an unpleasant taste with the chrysippus pattern. At this stage it would have been interesting to have offered it some well-known mimic of chrysippus, such as the female of Hypolimnas misippus or the trophonius form of Papilio dardanus, but this experiment was unfortunately not made. Marshall did, however, offer it at the same time a specimen each of Byblia ilithyia (a Vanessid) and of Acraea axina to which it bears a general resemblance. The baboon took the former but neglected the latter altogether. The general resemblance between the two species was not sufficiently close to deceive it.
These experiments with mammals, though few in number, are of unusual interest. Should they be substantiated by further work it is not impossible
that, as a factor in the establishing of a mimetic likeness, a stronger case may be made out for the monkey than the bird. The monkey apparently eats butterflies readily[[79]]: owing probably to a keener sense of smell it shews far less hesitation as to its likes and dislikes: its intelligence is such that one can easily imagine it exercising the necessary powers of discrimination; in short it is the ideal enemy for which advocates of the mimicry theory have been searching—if only it could fly. As things are its butterfly captures must be made when the insect is at rest, probably near sunrise and sunset, and this leads to a difficulty. Most butterflies rest with their wings closed. In many of the well-known cases of mimicry the pattern on the under surface of the mimic's wings which would meet the monkey's eye is quite different from that of its model. It is difficult in such cases to imagine the monkey operating as a factor in establishing a resemblance between the upper surfaces of the wings of the two unrelated species. On the other hand, some butterflies,
e.g. Papilio polytes, rest with wings outspread, and there are rare cases, such as that of P. laglaizei (p. 27), where the most striking point about the resemblance is only to be appreciated when the insects are at rest with their wings closed. In such cases it is conceivable that the monkey may play a part in the elimination of the non-mimetic elements of a palatable species which at the same time possessed a mimetic form closely resembling another species disagreeable to the monkey's taste. As has been pointed out earlier (p. [96]) even a slight persecution directed with adequate discrimination will in time bring about a marked result where the mimetic likeness is already in existence. It is not impossible therefore that the establishing of such a likeness may often be due more to the discrimination of the monkey than to the mobility of the bird.