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Posts tagged “Defense Mechanisms

Hickory Tussock Moth

 

Most tussock moths, such as this Hickory Tussock Moth (Lophocampa caryae), are densely covered with hair-like structures called setae that bear microscopic barbs.  Many people are sensitive to these setae and get an itchy rash if they handle a Hickory Tussock Moth.   Even touching the cocoon of a tussock moth can cause irritation, as the setae are woven into it.  Many tussock moths display warning coloration with their black, white, red, orange or yellow setae.  What looks like two Hickory Tussock Moth larvae in the photograph is actually one adult caterpillar (left) and its shed skin (right).   You can find these larvae feeding on hickory, walnut, ash, oak and many other trees in the woods right now.  After spending the winter pupating in a cocoon in the leaf litter, a small spotted, tan moth emerges.


Viceroy Butterfly

The Viceroy Butterfly closely resembles the Monarch Butterfly, but is smaller, and has a black line that runs across the veins of its back wings, which the Monarch lacks. While Viceroys don’t contain the poisonous cardiac glycosides that Monarchs do, they do contain salicylic acid due to fact that the larvae feed on willows. This acid not only causes the Viceroy to taste bad, but makes whatever eats it sick. So not only do these two butterflies look alike, but they discourage predators in the same way. This is not a coincidence. The fact that they are both toxic if eaten and are preyed upon by some of the same predators has led to their similar appearance. This phenomenon is referred to as Müllerian mimicry, and essentially it means if two insects resemble each other, they both benefit from each other’s defense mechanism — should a predator eat one insect with a certain coloration and find it inedible, it will learn to avoid catching any insects with similar coloration.