Fuzzy Wuzzy Was a Caterpillar

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As spring continues to march along, insects are abundant in all life stages.  While outside yesterday, yet another larva caught my attention as it walked along a concrete wall.  In continuing with our theme of caterpillars and their lookalikes, let's take a closer look.  The American Dagger Moth (Acronicta americana) caterpillar, shown below, belongs to the group of caterpillars known as "hairy caterpillars".

American Dagger Moth (Acronicta americana) caterpillar.  One of the "hairy caterpillars", this moth caterpillar feeds on the leaves of a variety of trees. (Click to enlarge)

Hairy caterpillars usually cause one of two reactions among people.  Most people are are fearful of touching them and find them weird to look at.  Some other people want to reach out and "pet" the fuzzy little critters.  Admittedly, they do not look like your typical caterpillars, but I don't think they look really weird.  Touching them; however, is rarely advised unless you know which species you're dealing with and how to handle such a caterpillar.  Many of the hairy caterpillars, like the Southern Flannel Moth (Megalopyge opercularis) and the Saddlebag Moth (Acharia stimulea) caterpillars can pack quite a sting.  As I always tell people when it comes to snakes, unless you're 100% certain of the identity of the species, treat it as though it is venomous. That means treat it with respect and give it plenty of space.  That does not mean kill it!  The same rule applies to caterpillars.  Don't know what it is?  Don't pick it up!

When a person comes into contact with the hairs (setae) of a caterpillar like the American Dagger Moth (Acronicta americana), the hairs break off of the caterpillar and imbed into the skin of the person.  These hairs are connected to glands just below the surface of the caterpillar's skin which produce toxins known to cause a variety of irritations to potential predators.  In this case, even a human simply wanting to touch the caterpillar is the potential predator.  A wonderful evolutionary adaptation, this sting causes the potential predator to leave in pain and allows the caterpillar to live to eat more leaves another day.  Unlike the intense burning pain that accompanies the sting of the Southern Flannel Moth or Saddleback Moth caterpillars, American Dagger Moth caterpillars mostly cause a small itchy rash that affects mostly people with sensitive skin.  Thus, not every person touching the American Dagger Moth caterpillar will feel the sting or feel the effects of the caterpillar's setae.

Notice the black tufts, pairs beginning at A1, then A3 and the single tuft at A8..  When you see that, you can immediately identify this caterpillar as an American Dagger Moth (Acronicta americana) caterpillar. (Click to enlarge)

On this particular caterpillar, the setae which are capable of "stinging" are the longer black tufts located on the back of the caterpillar.  These tufts are the identifiable characteristic of the American Dagger Moth caterpillar.  The head is always a patent leather black, but the overall color of the caterpillar can be lemon yellow, as with this caterpillar, or fade to white as they age.  The black tufts, on the other hand, will be consistent and are the definitive way to identify this caterpillar.  Notice the tufts appear in pairs at the first and third abdominal segments (A1 and A3) on the caterpillar, with a single tuft sprouting from the very end, abdominal segment eight (A8).  This single tuft is often referred to as a medial lash, as it isn't paired with another tuft or groups of tufts.

The caterpillars of American Dagger Moths feed on the leaves of Maple, Poplar, Willow, Hickories, Oaks and Alders, meaning you may very well be able to find them near you.  They are rather common in the eastern United States, but do occur fairly regularly throughout the western states.  So, by all means, get out there and start exploring!  Oh, and PLEASE use caution around these caterpillars!  If you do not know how to handle them, then don't!  Though it is usually fine if you let them crawl over you, I do not advise doing it and take no responsibility for any stings you may incur.  I'm not teaching you how to handle these caterpillars nor am I teaching you how to handle venomous snakes.  (My friend and attorney, Blaney Coskrey, III, Esq. would probably ask me to add, "Please do not try this at home!")

Also, please be advised that caterpillars occasionally fall out of the trees in which they are feeding.  If one should fall down your shirt, use the very best of care in getting it out.  Try not to come into contact with the back of the caterpillar.  I've spoken to people that thought a bug went down their shirt and swatted at it, only to imbed the hairs of a Southern Flannel Moth caterpillar into themselves.  I love nature and want you to get as much enjoyment out there as I, but always know things can happen and nature can be a pretty tricky place to be.