Thursday, September 28, 2017

What's That Caterpillar?

By Anna Autilio
Lead, Environmental Educator

If you’ve been seeing as many caterpillars lately as we have, you’re probably curious about who they are and what they’re up to. Below you’ll find a peek into the life history of five common caterpillars seen around the VINS campus this September. How many of these have you spotted? 

Red-humped Oakworm Moth (Symmerista canicosta)

Red-humped Oakworm Moth by Kyle Jones.
You may have seen this striking, striped, orange-headed caterpillar making its way through the leaf litter underfoot. In late September, the larvae of the Red-humped Oakworm Moth drop to the ground after feeding for a few weeks on beech, chestnut, and oak leaves. Once on the ground, they find a rolled up leaf in which to form a cocoon, and overwinter in this pre-pupal stage. Next June, they will emerge as an inch-long, ashen gray moth that lives only for 2 weeks, long enough to deposit 50 creamy-white eggs on the underside of an oak leaf, and start the cycle again. Although Red-humped Oakworm Moths are native, they are known to defoliate entire sections of forest during peak population years.



Isabella Tiger Moth (Pyrrharctia isabella)

Isabella Tiger Moth by Erika Mitchell.
This objectively adorable caterpillar is so well-known that many eastern US towns hold “Woolly Bear” festivals each summer. In fact, quite a bit of mystique follows the Isabella Tiger Moth caterpillar: they are believed to predict the severity of winter by the width of the brown stripe in the middle of their fuzzy body. This is not true, as the width of the band is only related to how old the caterpillar is. Despite being so fuzzy, these caterpillars are not venomous, and the hairs are not “urticating” or prickling, though they can cause a mild allergic reaction in some people. Picking them up is not recommended for this reason, and because when frightened, the caterpillars may “play possum” by rolling into a ball. The caterpillars are generalists, feeding on a variety of plants including plantains, dandelions, and nettles. After overwintering as caterpillars (they can survive being frozen solid), they emerge in the summer as a tiny yellow moth speckled with black dots.

Tussock Moths – Banded, Hickory, White-marked & Spotted (Family: Erebidae)

Hickory Tussock Moth by Susan Elliott
The bold and brazen tussock moths at VINS are seen confidently inching their way across parking lots, pathways, and trails. This may be because unlike the woolly caterpillar above, they are venomous (stinging), have urticating hairs, and are chemically protected—they are inedible because of alkaloids built up in their body from the plants they eat. They display this to would-be predators by being brightly colored, and sporting long, black tufts of setae called “hair pencils”. Tussock moths are late-season feeders on a wide variety of trees, including deciduous and coniferous species. Some, like the White-marked Tussock Moth, actually overwinter in the egg stage. When a female emerges from her cocoon, she sports reduced wings compared to the male, and does not leave the vicinity of her cocoon, laying the eggs right on top of it once she is fertilized.


Tiger Swallowtail (Papilio glaucus)

Eastern Tiger Swallowtail by Grae O'Toole.
The first known drawing of a butterfly in North America was of an Eastern Tiger Swallowtail. They are conspicuous butterflies, as they are large and relatively long-lived, producing two or three broods of eggs between spring and fall each year. But perhaps even more alluring than the butterfly is the caterpillar. Green-brown and pudgy, this caterpillar sports two perfect eyespots on the back of its thorax after its third molt. These eyes, combined with a pair of orange osmeteria near its head that produce a foul smell, make the Eastern Tiger Swallowtail caterpillar seem like a tiny snake. They even sway back and forth to complete the illusion, which is effective at deterring bird predators. Vermont is the northern edge of the Eastern Tiger Swallowtail’s range although we routinely see Canadian Tiger Swallowtails here, and the caterpillars spend the summer munching away at cherry, magnolia, and tulip leaves.


Monarch (Danaus plexippus)

Monarch by Judy Welna
Finally, the state insect of Vermont—the Monarch! This gorgeous animal is well-known as one of the milkweed butterflies, because of its reliance on the normally toxic plant. Just like the tussock moths, these caterpillars (and the butterflies they become) are aposematic, or brightly colored as a warning to predators against toxicity. A female butterfly may lay 300 to 1200 eggs on a milkweed leaf, which hatch into black, yellow, and white-striped caterpillars than can grow to be several centimeters long. Famed for their long migration to Mexico, due to habitat loss and herbicide use, Monarchs have been experiencing a long-term downward population trend. Many conservation societies are studying this worrisome development, and are pushing for government protection for these important pollinators.




Have we missed any of your favorites? Send us photos of the caterpillars you have seen this fall!

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