Monday, October 7, 2013

In defense of the lowly grape

The Riverbank Grape, Vitis riparia, one of our most common native plants. Unless you're a wine connoisseur, chances are you don't much care for wild grape. Most foresters certainly don't. They all too often regard the plant as a leafy vining scourge; a clambering liana that engulfs "better" plants like a vegetative amoeba. CLICK HERE and you'll see a bulletin from the Ohio State University's Extension Office that attempts to make the case that grapes are noxious, and alert interested parties to their perils. They make reference to "abandoned vines only", but I'm not sure what that means. Most grapevines, and the best most productive grapevines (using my criteria) certainly appear abandoned, untended, and thoroughly unkempt.

This is a close relative of grape, and another member of the Vitaceae family, Virginia Creeper, Parthenocissus quinquefolia. When it turns brilliant red in fall, people will take notice and ooh and aah, but for the rest of the growing season it's a meager notch or two above grape on the botanical social scale.

Yet these two species are highly productive when it comes to contributing to food webs, and play host to some of our most interesting herbivores. Birds galore feast on their fruit, or dine on the legions of insects that feed on the plants. Many insects, in fact, are totally wedded to plants in the grape family. Cerulean Warblers, recognizing the treasure trove of food spawned by grape tangles, seem to be rather intimately associated with grapes during the breeding season, even using the shreddy bark of the vines for nest construction.

Not long ago, some of us were poking around a scruffy woodlot in northern Ohio, when someone spotted this beast. On a grapevine. They paged me, and upon arrival I was pleased to see a beautiful Pandorus Sphinx caterpillar, Eumorpha pandorus. These tubular little grape specialists are cool by almost any reckoning, resembling little cylindrical terriers complete with stubby tail.

Only ten or fifteen away, on the same patch of grape, was a bigger, more mature Pandorus Sphinx. Caterpillars such as this go through five molts, or instar phases, before reaching maturity, and each instar can look quite different.

Caterpillars are eating machines, and this Pandorus was laying waste to the grape. It wouldn't have been too long after this photo was taken that the cat entered its pupa/cocoon stage. It will ride out the winter in that form.

If all goes well for the sphinx, this is what it will emerge as next year - an adult Pandorus Sphinx moth. They're jumbos, and this one was on the front of my office building in a very urban part of Columbus. But we've got some grounds which sport an unkempt woody patch with its share of wild grape, and with just a bit of habitat and host plants, such cool animals can be produced even in the asphalt jungle.

A few weeks back, I was in the wilds of Kentucky and did a lot of nocturnal prowling, as that's what it takes to find lots of caterpillars (and other COOL STUFF). We encountered an especially lush patch of Riverbank Grape, and like all good caterpillar-hunters, I paid close attention to the tangled vines. It wasn't long before one of our party let out a shriek - they had found a very cool cat indeed!

This shy little beast is a Beautiful Wood-Nymph caterpillar, Eudryas grata, and it is another in a long line of grape specialists.

Here's what it will grow up to be - quite a different animal than the caterpillar! Adult Beautiful Wood-Nymph moths are topnotch bird dropping mimics.

Further searching of the same Kentucky grape tangle produced yet another amazing bag of goo, seen here from afar. Usually it doesn't take to long when searching grapes in September - prime caterpillar season! - to produce some interesting subjects. This animal, as we shall see, is certainly an interesting subject.

I hooked the caterpillar down for a better look, and we were thrilled to see that it was a Hog Sphinx caterpillar, Darapsa myron. This animal is a good example of why people are increasingly getting interested in the larvae of moths and butterflies - they are often living objets d' art.

I dipped back into the files to produce this image of an adult Hog Sphinx, taken six years ago with much lesser camera gear than I now deploy (and fewer skills than I now have, probably). The moth is tattered and frayed, showing its age, but still is clearly a Cool Flying Object.

This little show just touches the tip of the Vitaceous iceberg of animal life spawned by the lowly grape. A book could be written on the ecological intricacies of these underappreciated plants.


Mary Huey said...

Thanks for the close-up look at these caterpillars and another reason to enjoy grape vines in the wild!

Unknown said...

Haha, I always love your posts, Jim. You've got a great way with words. I inadvertantly stumbled upon numerous cool cats this past month also, I wish I would have gone out searching at night! Never tried that before but I have been wanting to start taking night hikes to see what I could find. I totally share your opinion about the underappreciated plants and its nice to have you representing them for everyone!


Anonymous said...

I have wild grapes growing all over on my property. In fact, just recently I found a hog sphinx cat on my Niagara grapes.

@Doug: I would like to go on a night hike also. The only downside is the spiders. :)

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