Thursday, September 16, 2010

White-marked Tussock caterpillar

White-marked Tussock Moth caterpillar, Orgyia leucostigma, feeding on Witch-hazel, Hamamelis virginiana.

A few weekends ago, I had the good fortune to cross paths with one of our more beautiful caterpillars while exploring forests along Columbiana County's Little Beaver Creek. White-marked Tussocks aren't rare; in fact, they are probably one of our more frequent caterpillars. But, caterpillars aren't the easiest things to find, and a bit of serendipity often factors into discoveries.


These things are wackily ornate, with various pencil-brushes, bristling setae, stripes, dots and colors. I was with some people who had never seen a White-marked Tussock and they seemed suitably impressed. They probably would have been less than awed by the adult - the tussock morphs into a bland brown moth that is completely unremarkable.

These cats are tolerant of a diverse diet, and in addition to the Witch-hazel that we found it munching on, they'll snack on a wide variety of woody plants. Remember, butterflies tend to be connoisseurs, finicky and ultra-selective, often only accepting one species of plant for their larval chow line. Moths, well, they're usually garbage-heads. Other appropriate food plants common to the area where I found this bushy little larva are Black Cherry, American Elm, Yellow Birch, Hackberry, and various oaks and hickories. They'll even process Eastern Hemlock, a conifer!

Here's a theory I find fascinating. Those four pencil eraser-like white tufts are thought by some to create the illusion of brachonid wasp cocoons. The theory being that an actively hunting brachonid wasp would see them, and think one of her sisters had already gotten to the caterpillar, and thus would pass it by. This is really great stuff, and I love that sort of deception. But, I don't know that it's true.

But, judge for yourself. This is a Pawpaw Sphinx that I photographed in late summer that was parasitized by brachonid wasps. These wasps lay eggs on the caterpillar, and upon hatching the grublets bore within. Those little white cases are the grub's cocoons; their last stop before transforming into adult wasps. Prior to making these the ghoulish little wrigglers lived inside the caterpillar, eating it from within before popping from its husk like an alien horrorshow.

Look at the real brachonid cocoons, then scroll up and check out the White-marked Tussock.

Interesting.

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4 comments:

Dave said...

I call these guys the "toothbrush caterpillars"

Jana said...

When I glanced at the first photo, I immediately thought uh oh, it's already been parasitized. It sure does seem like a clever survival tactic.

Musicmom said...

I thought the same as Jana...

Danielle said...

haha neat. I had one of these fall almost into my lap last month sometime.