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PRI's Environmental News Magazine

Ode to Caterpillars

Air Date: Week of January 13, 2012

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Some people look at caterpillars and see creepy crawlers. Others, like biologist Dave Wagner, look at caterpillars and see gorgeous creatures that play an essential role in nature’s biodiversity. Producer Laurie Sanders has this profile.

Transcript

GELLERMAN: We look down on the lowly caterpillar, but our appreciation soars in the spring when it transforms into a lovely butterfly. Still, even before metamorphosis there’s a lot we can thank the creepy crawlers for - as Laurie Sanders reports.

[SOUND OF WHACKING VEGITATION]

SANDERS: With one hand, Dave Wagner uses a short stick to rap the branches of an alder shrub. In the other, underneath the leaves, he holds a beating sheet—a square frame with a piece of white cloth stretched across it.

[BEATING SOUND CONTINUES]

WAGNER: Many of these caterpillars are so well camouflaged that it’s almost impossible to pick them out with the human eye unless you know exactly what to look for and where to look. And, there’s not enough hours in the day to find caterpillars that way.


Dave Wagner collecting moths in Mohegan, CT. (Photo: Courtesy of Dave Wagner)

[BEATING SOUND CONTINUES]

WAGNER: Okay, lets’ see what we’ve got. Lots of insects. Mostly small beetles. There’s a caterpillar, look at that it’s a swallowtail larva. Gorgeous creature. Look at those eyespots. Let’s give him a little squeeze, and see if he sticks out osmeteria. Whoa. Look at that. Smell that. Pretty sweet.

So, I guess if a bird were to pick at those eyespots that you’re seeing here, those orange tentacles would come out, covered with sort of that goop- that orange citrus-y goop, and hit the bird right on the beak, possibly even go into the eyes. That’s its defense. Not to mention that it’s pretty well camouflaged, really.

SANDERS: Dave Wagner is a biologist at the University of Connecticut in Storrs, and a world authority on caterpillars.

WAGNER: I think there’s something really special about watching a caterpillar metamorphose into an adult. You never know what you’re going to get. So it’s a real life example of the Cinderella story, the ugly duckling, the phoenix from the flame. There’s something very powerfully engaging and metaphorical here, and I’m certain a lot of kids find much hope and interest in this change.


Composia fidelissima (Photo: Andy Brand.)

SANDERS: Wagner certainly does. During the last 20 years he’s raised tens of thousands of caterpillars, and in 2005, he wrote the first comprehensive guide to the caterpillars for eastern North America. The book became an instant hit among naturalists, and with Wagner’s colorful writing style, it also went on to win a literary award.

[WHACKING SOUND]

SANDERS: Today’s excursion is to a swamp in Petersham, Massachusetts. As Wagner beats the bushes, he’s careful to rap on only one plant species at a time. That’s because most of the 3,000 species of moths and butterflies found in New England are very specific about what plants they eat as caterpillars. And, Wagner says, of all the plants that are eaten, nothing is more popular than oak.

WAGNER: Oak is like type O blood. And so there are probably 400 species of butterflies and moths in New England that eat oak. Look what we have here this is a fabulous caterpillar. This is the caterpillar of a hooktip moth. What is really exciting or interesting and novel about this caterpillar is that he has two specialized setae near his rump that he actually uses to drum on the leaf where he is at. So this is one of the few talking caterpillars that I know about.

So these guys actually advertise to their brothers and sisters, their sibs, and perhaps any other caterpillars that ‘this is my leaf.’ And so they detect little vibrations and they will start using paddles on their rump basically to drum out a beat, a signal, which says “this is mine, find another.”

SANDERS: But to protect their own skins, Wagner says most caterpillars use shape and color. Some have gone the cryptic route—they’re green or look like sticks. Or bird poop. Or wilted leaves. Others have taken the opposite approach, and use bright colors—reds, yellows, and oranges—offset by blacks or whites to advertise that they have stinging hairs or toxins.

WAGNER: These are the Clint Eastwood caterpillars. Basically you’re a bad dude, and you’re trying to advertise to any would-be predator that perhaps you’d be better off looking elsewhere for a meal.

SANDERS: And all these caterpillars, bad dudes included, play a crucial role in the ecology of our landscape.

WAGNER: Springs would be very quiet in the northeast if it weren’t for caterpillars. They play a quintessential role in the diets of many animals, but particularly, we think, songbirds. And then as these caterpillars turn into adults, they play other roles. So the butterflies and moths that these caterpillars are going to turn into play quintessential roles in pollination, for example, they’re absolutely essential again in the diets of certain flycatchers, and bats.


Dave Wagner in San Rafael, Ecuador. (Photo: Dave Wagner)

SANDERS: And there’s another important role that caterpillars have played. Because plants can’t run away from caterpillars, they’ve evolved a battery of chemicals to protect themselves. Wagner says these secondary chemicals are the basis for drugs and medicines—like opium in poppies and salicylic acid in willows that’s used in aspirin. Others—like rubber and turpentine-- are used in industries. And then there are culinary benefits. Cumin. Paprika. Pepper. Cinnamon.

WAGNER: Indirectly our lives are greatly enriched by the fact that there’s caterpillars on this planet. French food and Latin American food--these would be absolutely bland if there weren’t plants manufacturing these chemicals to protect themselves from ravenous caterpillars.

SANDERS: So, the next time you tip back a glass of fine red wine, give a toast to caterpillars for the many ways they’ve influenced our lives - including the production of tannin - the natural chemical in grapes that gives wine its body and character. For Living on Earth, I’m Laurie Sanders.

 

Links

Owlet Caterpillars of Eastern North America by Dave Wagner

David Wagner’s Entymology Lab at University of Connecticut

 

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