Johann Friedrich Theodor Müller (German pronunciation: [ˈjoːhan ˈfʁiːdʁɪç ˈteːodoːɐ̯ ˈmʏlɐ]; 31 March 1822 – 21 May 1897), better known as Fritz Müller (Brazilian Portuguese: [ˈfɾits ˈmileʁ]), and also as Müller-Desterro,[1][2] was a German biologist who emigrated to southern Brazil, where he lived in and near the city of Blumenau, Santa Catarina.

Müller had what would be seen today as a normal scientific education at the universities of Berlin (earning a BSc in Botany) and Greifswald, culminating in a PhD in Biology.

As a result, he emigrated to Brazil in 1852, with his brother August and their wives, to join Hermann Blumenau's new colony in the State of Santa Catarina.

During this time, he studied the natural history of the sub-tropical Atlantic forest, around the Itajaí River valley.

He was one of many naturalists to visit and work in South America during the nineteenth century, but was the only one to settle in Brazil for the rest of his life.

It is an advantage for such potential prey to advertise their status in a way clearly perceptible to their predators; this is called aposematic or warning coloration.

The principle is of wide application, but in Müller's case the prey were butterflies, and the predators usually birds or reptiles.

[7] In Müllerian mimicry, an advantage is gained when unpalatable species resemble each other, especially when the predator has a good memory for colour (as birds, for instance, do have).