Caterpillars, the larvae of butterflies and moths (Order Lepidoptera), are exquisite creatures that display an array of colors, patterns, and interesting behaviors. Although some species are considered pests in our gardens and forests, they are extremely important in terrestrial food webs, serving as the primary food source for many of our resident and migrant songbirds. Without caterpillars, our forest would be silent in spring. Caterpillars also play an important role as macrodecomposers by shredding and consuming leaves which helps to accelerate the nutrient cycling process. Fall is a great time of year to hunt for caterpillars. Some species, like the familiar wooly bear (Pyrrharctia isabella) pictured below, can be found roaming about in search of a hibernaculum, such as your wood pile, where they overwinter. Not only is caterpillar hunting good sport, it can give us a greater appreciation for the little creatures that go unnoticed around us.
One doesn’t have to travel to some far away exotic place to find caterpillars. They can be found right in ones backyard along forest edges, fields, and gardens. Many species have evolved cryptic coloration and behaviors that can fool even the most intelligent predators (including caterpillar hunters). The first step to finding caterpillars, or for that matter any insect, is to walk more slowly, observe more closely, and magically they will start to appear as you develop a “search image”. Rarely will the caterpillar be sitting exposed on the leaf surface, so be sure to examine the underside and along the leaf margins, stems, and on flower heads. A more efficient method is to use a beating sheet or “drop cloth”. This can be as simple as using a white bed sheet, or umbrella, and placing it under a limb of a tree or shrub and hitting the limb with a stick to dislodge the caterpillars from the foliage. In addition to caterpillars, a multitude of other species including jumping spiders, ants, beetles, and stinkbugs can be found on the sheet, but that is another story. One word of caution, be careful when handling spiny or hairy caterpillars, as the hairs of some species can cause an allergic reaction to some people.
Once you find a caterpillar, the next step is figuring out what it is and learning about its life history. Questions like: What does it turn into? What does it eat? What is its range? Is it a pest in my garden? These questions can best be answered by referring to a field guide of the caterpillars occurring in your area. An outstanding guide is “Caterpillars of Eastern North America” by David Wagner, which will enable you to identify just about any species you will find in your backyard or in our region.
Provided below are some photographs I recently took during a caterpillar hunt in Deering, along with a few brief comments. If you find any caterpillars that you would like to share, please don’t hesitate to email images to email@example.com.
Polyphemus Moth (Anthera polyphemus)
You can imagine my excitement when I turned over the leaves of a sugar
maple and found this spectacular fluorescent green silkmoth caterpillar. It has been reported that Polyphemus caterpillars sometimes make a snapping sound with their mandibles.
Great Ash Sphinx (Sphinx chersis)
White Ash (Fraxinus americana) is a common tree in Deering, so it comes as no surprise to find this large ash-feeding species. However, this may quickly change now that the invasive emerald ash borer (Agrilus planipennis) has been detected in town (2017). This beetle has already killed hundreds of millions of ash trees in the eastern United States. Infested trees die quickly; within 3-5 years. For more information about this destructive forest pest and what you can do, please refer to nhbugs.org. It’s sad to think that if we lose our ash trees, we may no longer see the Great Ash Sphinx, or the other species that depend on ash for their survival.
Monkey Slug (Phobetron pithecium)
One of the strangest looking caterpillars I have ever encountered, with its slug-like body. I was lucky to find two monkey slugs on the same day; one on cherry and the other on oak in a field. It’s hard to imagine what this bizarre creature is trying to look like.
Wooly Bear (Pyrrharctia isabella)
Perhaps one of our best known caterpillars, it is frequently seen this time of year crossing roads and driveways. I remember as a child being told that the width of the orange band can predict the severity of the coming winter. It turns out the width of the band is quite variable, increasing in size as it molts.
Red-humped Oakworm (Symmerista canicosta)
This is a good year for red-humped oakworms, as caterpillars were found in just about every beating sample from red oak. The caterpillars start life as gregarious feeders forming large clusters on the underside of leaves and become solitary in later instars. They have been known to cause widespread defoliation of oaks, especially in the northeast. Full-grown caterpillars drop to the ground in late September and pupate in the leaf litter.
Southern Oak Dagger Moth (Acronicta increta)
The color of this caterpillar is variable, ranging from green to a beautiful salmon-pink, with pairs of white spots on top of the abdomen. It was found resting on the underside of a red oak leaf in a characteristic position with the head bent back along the abdomen. This moth is a part of a difficult species complex making identifications quite challenging.
Unicorn Caterpillar (Schizura unicornis)
This caterpillar is aptly named for its unicorn-like horn on its abdomen. A master of camouflage, it is easily overlook when mimicking the edge of a partially eaten leaf. It feeds on a wide range of trees and shrubs, including cherry.
Hickory Tussock Moth (Lophocampa caryae)
The common name of this moth is somewhat misleading, as it feeds on a number of trees species other than hickory. In fact, I’m not aware of any hickory growing in the area where this caterpillar was commonly seen feeding on white ash, red oak, and birch. The hairs of this species can cause an allergic reaction in some people.
Banded Tussock Moth (Halysidota tessellaris)
One of the few caterpillars in our area that will rest entirely exposed on the upper surface of the leaf, suggesting they are distasteful to birds. This caterpillar is a generalist, feeding on many species of woody shrubs and trees.
Eastern Tiger Swallowtail (Papilio glaucus)
Its life as a caterpillar is nearly over, as it prepares to pupate and overwinter as a chrysalis. Just prior to pupation, the caterpillar turns from green to dark brown and spins a silken girdle around the thorax to hold the chrysalis in an upright position.
Gray furcula (Furcula cinerea)
A favorite among caterpillar hunters with its long anal prolegs that resemble a forked tail. when disturbed, the larva raises the erect ‘tail’ above its body in a threatening-like manner. It was found feeding on a poplar along the edge of a field.