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False Head Hypothesis

Tags: butterflies, Peggy Notebaert Nature Museum, Chicago Academy of Sciences, camouflage

Published On 4/25/2013

I recently posted this butterfly photo on line:

It's a Ciliate Blue from Malaysia.  A friend was prompted to comment, "I like the orange and black "eye" on the edge of the wing. Is it part of a disguise camouflage?" 

My friend was very astute in noticing that the spot resembles an eye and surmising that it has something to do with defense against predators. This species is a good example of what is often referred to as the false head hypothesis. The hypothesis notes that the markings on one outer edge of the hind wings resemble heads in some species of butterflies.  These markings can be quite elaborate in some cases and may include tails that resemble antennae and a narrow shape that enhances the appearance of a head.  Some species carry this even one step further and rub their hind wings together.  This draws attention to the tails, which appear like twitching antennae.

Gray Hairstreak (Strymon melinus)

The false head hypothesis suggests the possibility that these head-like markings confer a survival advantage by deflecting predator attacks towards the hind wing (which butterflies can usually live without) and away from the vulnerable head. Many butterflies, especially species in the Metalmark and Gossamer-Winged Butterfly families show these markings.

Martials's Scrub Hairstreak (Strymon martialis)

In 1980, scientists from the Smithsonian attempted to demonstrate that predators could be fooled into attacking the wrong end of the butterfly. They collected hundreds of butterflies in Panama and Columbia, and divided them into groups based on the number of head-like features were present in their wing patterns. Consistent with the false head hypothesis, the greater the number of head-like features, the more likely wing damage due to predator attacks was to be directed to that part of the wings.

Eastern Tailed Blue (Cupido comyntas)

The false head hypothesis remains a hypothesis. Further support of the hypothesis would require a much more difficult experimental design - one that demonstrates that butterflies with the false head designs survive better than those without them.

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