Müller, F. (1878) Über die Vortheile der Mimicry bei Schmetterlingen. Zoologischer Anzeiger 1: 54-5
Fritz Mülller (Itajahy, Brazil)
On the advantages of mimicry in butterflies
(Translated by Jochen Jaeger, Carleton University)
It is odd that sometimes you think a lot about questions for several years for which the solution is so easy that you hardly understand how it was possible to find difficulty in it for an instant. This is what happened to me with mimicry in butterflies. Danaines, iIhomiines, Acraeines, and Heliconiines all appear to be protected to the same degree by noxious smell and taste. However among them there are a lot of imitating species. Especially strong is the smell of the Eueides species; however Eueides pavana is a copy of Acraea thalia, E. isabella is a copy of Helic. eucrate or of Mechanitis lysimnia, and E. aliphera is similar, apart from size, to Colaenis julia.
- What advantage can such species, protected by bad smell, gain from the fact that it is similar to another species that is also protected? - When its predators avoid it because of instinct then there is no advantage; if however, and this is anyway the more probable case, its predators first have to learn that it is unpalatable by experience, it will have an advantage that is the greater the less numerous it is. The gain that two unpalatable species have from their similarity behaves as the reciprocal of the square of their numbers of individuals.
- Instead of a general deduction, which is by the way extremely simple, I give an example. There may in a certain area live two unpalatable species; 10,000 individuals of the first species, and 2000 of the second. The predators living in the same area may eat per year 1200 individuals of each [distinct] unpalatable species per year until they avoid it as such. Each species would lose this many if they appeared different; but if they are very similar so that experience with one species benefits the other, then the first species will lose 1000 and the second 200 individuals. The first species therefore will gain because of its similarity 200 individuals, or 2 % of the total number, the second will however gain 1000 individuals, which is 50% of the total number - from this consideration it follows further that probably in some cases (for example Thyridia and Ituna) the question which one of both species is the original and which one is the copy is an irrelevant question; each had an advantage from becoming similar to the other; they could have converged on each other.