Friday, November 6, 2015

Sluggish Moth Larva

Aside from falling leaves, this time of year doesn't provide a lot of color.  This light green spot stood out in contrast to the bare branches of small trees in the woodland timber stand improvement opening.  The flattened shape is distinctive, the physique that only another slug moth could love.

This is a Crowned Slug Moth caterpillar, Isa textula.  It feeds on elms, hickories, lindens, maples, oaks, Prunus species plus shrubs that are plentiful in our oak-hickory forest.  Viewed from the side, it looks like it was run over by a fat squirrel.  Its movement is sluggish even when prodded with a twig.  It depends on its hollow stinging hairs filled with a toxin for defense against predators and aging naturalists.  These spines called setae are described as "urticating," meaning that they cause an itching or stinging if you brush up against them.

Although lots of caterpillars have setae, not all are hollow or contain toxins.  The very appearance of spines probably deters many predators and if you come across them in nature it is probably better to use no touch techniques for collecting them unless you know the species.  An example of harmless setae is on the woolly bear described recently.

Crowned Slug Moth -  Jon Rapp
Southern Flannel Moth - Jon Rapp

Many of the moths arising from urticating caterpillars are common but so nondescript that you would not give them a second glance at your porch light.  The Crowned Slug Moth is no exception.  On the other hand a close inspection can reveal a lot of personality if not beauty.

Consider this Southern Flannel Moth above, Megalopyge opercularis, photographed by our friend, Missouri photographer Jon Rapp.  It has a furry coat on its wings that could start a major protest by PETA.  Its caterpillar below even has its own name, the derogatory title Puss Caterpillar.  Despite its soft and fluffy appearance, its hairs can sting you so do not pet it.  Read Jon's comments here.

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