Nettle-eating caterpillars

It's been a whirlwind the past few days. I left Columbus at 1:00 am last Friday morning, and drove about seven hours due east, to Millersville, Pennsylvania. Destination: Millersville University, home of the Native Plants in the Landscape Conference. This was its 20th year, and my fourth time to visit. The event draws upwards of 300 people every year, and always sports an interesting slate of speakers, and a gymnasium packed with native plant vendors. I was there to give the Friday night keynote, and then another breakout session talk the following morning.

The reason for my early morning departure was this guy, Dr. David Wagner of the University of Connecticut. Dave was giving the Friday morning keynote, and I really wanted to hear his talk. Wagner is the foremost expert on caterpillars, and has published two ground-breaking books on lepidopteran larvae, which can be found HERE and HERE. These books are fascinating windows into the world of some of our most interesting and beautiful insects, and I highly recommend them.

On Friday afternoon, escorted by botanist Tim Draude, we were able to visit a nearby park and look for bugs. As might be expected, we found many, including some very cool insects, and I made many photos. In the picture above, your narrator (left) and Dave Wagner stand by one of our more maligned native plants, which scarcely shows up as most of its foliage has been eaten away. If you look closely to the right of Dave's collecting sheet, you'll notice numerous little tubular squiggles on the plant stems.

Here's a closer view of the plant in question, which is tall nettle, Urtica dioica ssp. gracilis (grrr, I dislike plant varieties being labeled as subspecies). Tall nettle is just that, and these luxuriant plants towered to five feet or so in height. There were scores of the nettles throughout the park, and all of them were densely colonized by these caterpillars, which should show up a bit better in this shot.

And here's one of the nettle-feasters up close and personal. It's rather dark and plain, although some of the older specimens were prominently slashed with creamy-white stripes, and all of them were beset with columns of spines. If you can evolve your way into it, it is probably rather advantageous to have a diet of stinging nettle if you are a caterpillar. And this plant surely can put the hurt on us mammals. Swipe your hand through a stand of it and you'll learn quickly about the wonders of urticaceous hairs. These hairs are hollow and full of chemical irritants. When contacted, the brittle hair tip snaps off leaving a sharp point that jabs whatever brushed it, and in go the itch-producing compounds.

Most animals, us included, quickly learn to avoid nettles, and the plants' toxicity probably affords these caterpillars some degree of protection against predators.

Those nettle-eating caterpillars - at least those that survive - will morph into this gorgeous butterfly, the red admiral, Vanessa atalanta. That's right, weedy nasty stinging nettles are the host plants for this stunning insect. Much of not all of the eastern U.S. experienced enormous numbers of red admirals; an invasion the likes of which has seldom been seen before. I wrote about this phenomenon HERE.

Nettles may be much despised by people, but nearly all of them that are found in these parts are native species, and clearly contribute to the production of animals that we enjoy.

If you want to learn a lot more about native plants, their relationships with animals, including caterpillars, attend the Midwest Native Plant Conference! It is held in Dayton, Ohio, and the dates are July 27, 28, & 29. David Wagner is one of the speakers, and there'll be field trips and opportunities to see caterpillars, plants, and much more in the field. All of the details are RIGHT HERE.

Red Admiral Invasion

I'm freshly back from an interesting trip to the great state of Virginia and the beautiful city of Winchester - renowned for its Shenandoah Apple Blossom Festival. This event will celebrate its 85th year in a few weeks; unfortunately given the early spring, their apple trees will have shed their blossoms by then. I was there to speak at a new and interesting conference called Tomorrow's Landscapes, held at Shenandoah University. It was fun and infomative; among the better run of these sorts of things and it was great to see acquaintances such as Jeff Lowenfels all the way from Anchorage, Alaska, and Doug Tallamy from Delaware.

The relatively short drive over to Winchester took me through five states: Ohio, Pennsylvania, West Virginia, Maryland, and Virginia. Before leaving Ohio last Friday, I was seeing LOTS of red admiral butterflies, Vanessa atalanta. I saw some more along the drive to Virginia but not as many as were fluttering around my home state.

Bold and pugnacious, a showy red admiral alights on your blogger. These brush-footed butterflies stage periodic large, conspicuous northward migrations, such as happened over the last week in Ohio and elsewhere in this part of the country.

One day last week, I glanced out my office window - I work in a very urban area - and six or more of the butterflies were swirling around the blossoms of a flowering crabapple tree. I was even seeing red admirals flying through traffic on very busy Morse Road. Our Ohio Birds listserv was awash in comments about the proliferation of these butterflies, so much so that I was awaiting the appearance of one of the self-appointed listserv police, to make one of their bah humbug "those aren't birds!" comments.

A red admiral at rest with its wings held up is not nearly so conspicuous as they are when the wings are spread and flattened, revealing the showy orange-red bands. In fact, in this position, the butterfly becomes an outstanding leaf mimic.

Dave Horn, an entomologist and current president of the Ohio Lepidopterists, made the following statement on our Ohio Birds listserv in response to all of the red admiral reports: " The red admiral has periodically appeared in large numbers since the early 19th century. While there is no universally accepted explanation for these increases it seems most likely that they are related to high overwintering survivorship in the southern USA followed by favorable conditions for northward movement. This year we have had both a very mild winter (in Ohio and southward) and an early spring and I suspect the large numbers we are seeing reflect those weather conditions".

Sums it up nicely, I think.

Red admirals, in all their beauty, are spawned from plants in one of our most maligned botanical tribes, the nettles. I made this photo a few years ago, of a communal "nest" of red admiral caterpillars that had formed a tent shelter from the leaf of a tall nettle, Urtica procera. At least during their early instars, the caterpillars congregate within the rolled-up leaf, emerging under cover of darkness to ravage the nettle foliage.

Here's a red admiral chrysalis, which I also found on a nettle plant. I've found red admiral caterpillars several times, always on nettles. And always the stinging species. Not everything in the Urticaceae (nettle) family has stinging hairs, and apparently red admirals utilize non-stinging species, but I've only found them on the plants that you'll quickly regret brushing up against.

Not a bad strategy, if you can evolve yourself into it. Most critters probably shun nettles, same as we do, and that includes potential caterpillar predators.

Knowing that such a stunning butterfly as the red admiral requires the lowly nettle as an essential part of its life cycle might stimulate one to view these stinging plants with a fresh perspective. The plant in this photo is a tall nettle, Urtica procera - same species that I've found red admiral larvae on - and it isn't so ugly after all.

Plant some nettles in your yard and who knows, you might raise a crop of admirals. Or better yet, as I believe it is the Weedpicker who says, sneak into your neighbor's yard and plant them there - that's close enough to still enjoy the butterflies!