Sunday, July 27, 2014

Caterpillars Are Life

Caterpillars are not icky worms with legs that poop on your sidewalk. [Well, they do poop on your sidewalk but think of that as free fertilizer as you sweep it into the adjacent flower bed.]

American lady caterpillar on Antennaria

Caterpillars are life – life for beautiful flying creatures as their larval form ... and all that depend on them.

After a recent talk at the Cullowhee Native Plant Conference about caterpillars, I am energized and prepared to identify and appreciate more caterpillars than ever.

Background: As most of you know, caterpillars are the larval form of butterflies and moths (Lepidoptera). Local insects like Lepidoptera have evolved over time with their local ecosystem and the relationships they have with organisms like plants are both necessary and complex.

David Wagner from the University of Connecticut presented his topic “Native Plants, Caterpillars, Birds – A Story of Connected Fates” on Friday morning to the main group. David is author of “Caterpillars of Eastern North America,” now in its 8th printing since 2005.

His talk was lively and informative, a reflection of his keen interest in and knowledge of caterpillars. Some of the things I learned:

  • Specialization on certain plants matters. 80% of Lepidoptera are specialists, eating just one or within a small set of host plants. Some specialize on just a part of the plant! As a result, changes in populations of a plant can affect the population of the insect as well. 
  • Some don’t eat things that you’d expect: about 50 species only eat dead leaves on the ground, and some (such as the Harvester on page 92) eat aphids that live on plants. Some adults don’t have working mouth parts, they only use their adult phase to breed. 
  • A lot of work goes on after dark. Some caterpillars come out at night to eat (such as the Spicebush Swallowtail) and some moths only visit flowers after dark. He showed us this video about the comet orchid that attracts a special moth with a long proboscis. It is a moth that Darwin predicted would exist and which was finally found 150 years later with an infrared camera and lot of patience. 
  • There are Lepidoptera that are “diet mixers,” wandering around and eating different things even as a caterpillar. 
  • Caterpillars that specialize sometimes evolve to resemble the host plant. He showed us some marvelous examples of pine/juniper specialists that indeed resemble the foliage (like pine needles – long, slender and green with thin stripes). Why does that matter? It helps them hide from predators like birds. 
Owlet caterpillars on Solidago

Tasty looper caterpillar on Lobelia
And that brings us to the third piece of the relationship (and the talk). Birds eat caterpillars and for some birds they are a significant source of food, if not as an adult then certainly as a nestling.

If you love having birds in your yard then you need to love having caterpillars. Let out a big cheer every time you find a new one!

After the talk I bought David’s book and I’ve been reading a section at a time: the slug caterpillars, the loopers, the inchworms, the brushfoots, the hawkmoths, the prominents, the tussocks … each section covers a different group.

Snowberry clearwing on Lonicera (honeysuckle) - check!

I like that each species includes a list of common foodplants. I love that there is an index by foodplant! So if you see something eating on a particular plant, you can look for it that way. Want to know what's eating your honeysuckle ... look it up.
Spicebush swallowtail on Lindera - yep!

Selected ones include a picture of the adult as an extra feature but all include at least a picture of the caterpillar.

Fall webworms

I learned that fall webworms are the ones I usually notice; eastern tent caterpillars build nests in tree crotches while webworms engulf the branch. Some caterpillars like tussock moths glide to a new place to eat on a thin strand of silk (you've seen this right?); this is called ballooning.

Anisota virginiensis - wish I'd see it alive but there are probably
plenty more up there in the oak trees.
Some of them are gorgeous! Look at this pink-striped oakworm (which was dead when I found it). Nature is amazing.

While I see a lot of caterpillar evidence in my garden (chewed leaves, frass/poop), I don’t often find the actual caterpillar.

With both wasps and birds (as well as other critters) being predatory on caterpillars, I like to think that not seeing many means the ecosystem is in pretty good balance.

So next time you see a caterpillar, don't think of it as icky or creepy ... think of it as LIFE. And don't worry about chewed leaves, they grow back just fine.

P.S. This is my 200th entry on this blog. Thanks for all your support!


  1. I love this post! Thank you.

    I got Wagner's book when it first came out and it's wonderful. His is really the first comprehensive guide of caterpillars that I ever found. My only wish is that there was some sort of guide (perhaps an affiliated web site?) where you could type in the color of the caterpillar and whether hairy or not, plus the host plant and general location, then get a list of potential possibilities....


  2. Excellent topic for a 200th post! Cynthia, has a pretty good ID guide. Asks more questions than I have answers for sometimes, but it can definitely get you in the neighborhood.

  3. Ellen congrats on 200 posts. I am just seeing butterflies finally so I hope to find caterpillars soon!!