Thursday, August 4, 2011

Müllerian Mimicry

On 2 August 2011, Erika and I found both Viceroy and Monarch butterflies in Carleton College's arboretum. Note the distinctive line across the hind wings on the Viceroy above. Despite their similar patterns, the Viceroy and Monarch are not closely related. Although both are in the same Family, Nymphalidae, the Viceroy is in the genus Limentis (the same genus as the Red-spotted Purple.)  The Monarch is in the genus Danaus
For over 30 years I've taught that these two butterfies are examples of Batesian mimicry.This type of mimicry is when good tasting creatures look like poisonous ones. Because Monarchs store toxins from milkweeds, they are distasteful, if not poisonous to birds. The good-tasting Viceroys just have to less common than Monarchs, so that the birds to not catch on to the Viceeroys' disguise. But researchers have discovered that Viceroys contain their own distasteful chemicals. These distasteful butterflies have come to look alike, so as not to overly tax the birds' learning abilities. The birds only have to learn one pattern.  This convergence, where toxic critters look similar, is called Müllerian mimicry. 

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