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Filed under Outdoor Notes

May 30, 2011

This time of year, I often come upon Viceroy butterflies (Limenitis archippus) in low swampy areas with plenty of alders and willows.

Viceroy butterfly

Viceroy butterfly

The Viceroy is well known as a mimic of the Monarch (Danaus plexippus). Monarch larvae feed on milkweed, a plant that contains chemicals (cardiac glycosides) that make predators sick. For years, this was considered a type of Batesian mimicry, wherein the mimic does not share the property that benefits the species being mimicked.

However, recent research would seem to indicate that the Viceroy, like the Monarch, is at least a little sickening. Researchers have found that birds rejected the abdomens of Monarchs and Viceroys at about the same rate.

Such shared properties are known as Mullerian mimicry. I don’t know how the Viceroy acquires its unpalatability. The larvae feed on willow, which contains the basic ingredient for aspirin (salicylic acid). Perhaps birds don’t like the taste of aspirin; I don’t.

It can be somewhat difficult to tell Monarchs and Viceroys apart. Viceroys tend to glide; Monarchs flap more. Hereabouts, I have never seen a Monarch before early July. I often see Viceroys by mid-May. For visual confirmation, look at the hind wing. On the Viceroy, there is a dark line, about in the middle of the orange portion of the wing,  that parallels the trailing edge of the wing.  The Monarch lacks this line.

Monarch Viceroy comparison

Note the black line on the hind wing of the Viceroy

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One Response

  1. Dennis Murphy said:

    John, there are some great photos here. I’ll have to come to the site more often. I learn something every time I do.

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