Tag Archives: caterpillars

Hungry Hungry Caterpillars

Throughout much of New York State earlier this summer, fuzzy caterpillars were rampaging through natural forests and well-kept gardens alike. Maybe you noticed these bristly little critters wobbling along, or even had an itchy rash after touching their mildly stinging hairs!

These crazy caterpillars are Lymantria dispar, which you may have called gypsy moths in the past. Why not just call them gypsy moths? What is really in a name?

This is an exciting time as we wait to hear the new official common name for our moth, Lymantria dispar, but for this blog post we’ll call them L. dispar for short. Currently, the Entomological Society of America has is considering options for new names under the Better Common Names Project, in order to “bar names referencing ethnic or racial groups and names that might stoke fear.”

There is a plethora of fun characteristics for this moth which could apply to a new name. I personally vote for something akin to “Pricklecater,” “Blue-Red Spotted Messworm” or “Itchy Eww Moth.”

A L. dispar caterpillar up close.

Anyways… back to our story.

A native of Europe, L. dispar were accidentally released into the wild in 1869 and have since become “naturalized” in 19 Northeastern states. This means they have shoved their way into local food webs as they munch down on foliage then in turn become a tasty food source for birds, bugs, and other predators.

For the most part, they are active participants in the wonderous world of ecology. They are citizens playing their part in a complex and everchanging ecosystem. A single L. dispar caterpillar can eat about a square meter of plant material during its short lifetime, but one caterpillar doesn’t do too much damage.

The problem is that one female moth can lay more than 1,000 eggs in a single mass, which stick to the sides of trees, and are browish and gummy-looking.

That’s a lot of eggs!

The female moths, which are white, lay their egg masses on the sides of trees after mating. The masses are brownish and gummy in appearance.

Every 10 to 12 years, the L. dispar population explodes exponentially and hundreds of thousands of tiny caterpillars hatch in the spring. Once hatched, they use a strand of silk to “balloon” away on the wind until they find a newly leafing tree to eat and eat and eat.

To experience these numbers, I’d like you to imagine walking your favorite path in the woods. Shaded from the hot sun, you can hear the gentle pitter-patter of rain sprinkling down through the canopy. How peaceful… There is no better place in all the world on this cloudless day.

“Cloudless day? But isn’t it raining?” you ask.

Oh yes, something is raining down… but it’s not water.

Scientifically known as frass, this tiny spherical poop from thousands of very hungry caterpillars is dropping down onto your head and shoulders, as these little machines diligently convert the lush green leaves overhead into little brown balls of poo.

Not great. Pretty gross.

These baby caterpillars have small, young jaws, and prefer soft new budding leaves until they are old enough to chew tougher vegetation. While they prefer hardwood trees, they will eat more than 300 different plant species when hungry enough, stripping away all foliage until trees and bushes are left embarrassingly naked.

This can be a problem.

Caterpillar can strip away much of leaf material. Usually, trees can survive it, as long as it does not happen too many years in a row.

When deciduous trees like oak, birch and maple are eaten by caterpillars, they usually have enough stored energy to push out another set of leaves before the summer is through. It takes multiple years of defoliation to weaken these trees to the point of death. However evergreen trees cannot bounce back as quickly. Coniferous (evergreen) trees put lots of energy into their tough, thick, needle-like leaves, and will likely die if more than half of their needles are eaten.

Most years the caterpillars are fairly harmless, except during these incredibly destructive outbreaks which reoccur in a slow but disastrous cycle. Due to this pattern, L. dispar are considered cyclical pests.

In the adult stage L. dispar moths are not destructive at all, as they do not eat anything (no digestive system) and only live for a few days. The white fluffy females have pretty wings used for decoration rather than flying, and release a hormone into the air for male moths to find them. Females remain on the sides of trees as the males fly in search of the females’ scent.The female will lay fuzzy egg masses on whatever surface she’s near and the life cycle will begin again.

This is where we can take some control over the situation. By counting the egg masses in the wintertime, we can predict how many L. dispar caterpillars will hatch in the Spring and we can prepare a plan of defense. 

Natural Population Controls


While major L. dispar outbreaks can resemble a plague of locusts consuming everything in their path, nature often has a way of correcting imbalances. At low densities, vertebrate predators keep the population in check, but are ineffective at controlling massive numbers of prey. Bird bellies just aren’t big enough!

However, when L. dispar caterpillars are densely packed into one area, viruses and funguses can spread rapidly. These are naturally occurring diseases which are always present in the environment, but only take significant effect when populations are grossly out of control. Researchers have identified one virus specialized to L. dispar which kills 90 percent of infected caterpillars. This virus has since been converted into an effective treatment which brings the population down to healthy levels.

This natural method of population control is the preferred way to control the situation since it doesn’t harm any other species. However, this treatment must occur very soon after the caterpillars hatch, otherwise the damage will already be done.

These last few months we’ve seen many caterpillars eating their way through New York, and next year could be even worse in some places… or not. It all depends how well nature’s natural defenses have worked.

Measures are being taken at State Parks to perform egg mass surveys to try and predict next year’s population and prepare for any treatments accordingly. Let’s not repeat the summer of 1981 when 13 million acres of forest were defoliated! Our poor defenseless trees!


Post by Juliet Linzmeier, Student Conservation Association member, Invasive Species Unit, NYS Parks

Cover shot – A L. dispar caterpillar. All shots from NYS Parks.

A close-up of a female L. dispar moth.

Resources

DISCLAIMER: The following materials have not been updated on the new common name for L. dispar, and refer to this pest as “Gypsy Moth”.


Want to learn more about these moths and efforts to protect the forest? The DEC has great information here at Gypsy Moth – NYS Dept. of Environmental Conservation

Prefer watching videos? The DEC also did a 30-minute Facebook Live post, which covers the history, morphology, control methods, and more!


Magnificent Moths

Black-Waved Flannel Moth
The fuzzy, stout body is typical of moths. This black-waved flannel moth (Lagoa crispata) is uncommon in New York. Photo: M. Schlesinger, NYNHP

It’s National Moth Week! So let’s learn a little more about them.

Moth or butterfly?

Moths and butterflies are members of the order Lepidoptera (Greek for scale and wing). Most butterflies have club-shaped antennae – a thin stem with a ball at the end – whereas moths usually (but not always) have feathery antennae like the luna moth above. Moths often have fuzzy, short bodies compared to the more slender, smoother body of butterflies.

Luna Moth
The Luna moth (Actias luna) is one of our largest moths. Photo: K. Smith, NYNHP

Are all moths small and brown?

Many moths are small and brown, tan or white. But many are much fancier; in fact you may have mistaken some colorful ones for butterflies. Sometimes the colors are hidden while the moth is at rest, but revealed when in flight, like the tiger moth. The silk moths are spectacular in size and color – such as the Luna moth above.

How many different kinds of moths are in NY State?

There are over 1,000 moth species in the state. A single State Park can harbor dozens to hundreds of different species of moths. Larger parks and those with rare habitats are great examples of places that support a diversity of different species of moths. To date, scientists have identified about 90 species in Watkins Glen and Taughannock State Parks, over 300 species in Minnewaska State Park Preserve, and nearly 500 species of moths each at Hither Hills and Napeague State Parks!

Sphinx Moth
The sphinx moth – or hawk moth – can be mistaken for a hummingbird. Look for them hovering over flowers. There are many species in this group of moths. Photo by T. Weldy, NYNHP

Where and how do you find moths?

Most moths fly at night. The easiest place to see moths is at a porch light or around the lights of campground buildings. For better viewing hang a sheet or light colored cloth up with a light next to it. The moths will land on the sheet (see below) so you can get a close up look without even touching them. Other moths prefer daytime or can be seen resting during the day.

Tim McCabe
Moth expert Tim McCabe from the NY State Museum examines moths that were attracted to the light during a survey in Taconic State Park. Photo by George Heitzman

Why are those moths in boxes?

A lot of moths are difficult to identify. So scientists collect and preserve specimens in order to look at them closely to identify them. Collections are also important as a permanent record of what species were found at a site. Each specimen is labeled with location, date, and species name. Then the specimens are placed in ‘safe storage’ in a museum such as the New York State Museum or a university collection where they can be used for other research or study.

Are there rare moths in State Parks?

Yes!  For example, four rare moth species have been found in Minnewaska State Park Preserve and over 30 rare moth species have been documented in Napeague and Hither Hills State Parks on Long Island. Some have fun names like fawn brown dart (Euxoa pleuritica), pink star moth (Derrima stellate), chocolate renia (Renia nemorali) and black-bordered lemon moth (Marimatha nigrofimbria). Most areas of the state have not even been surveyed for moths, so there is much more to learn. Currently, over 100 species of moths have been identified as rare in the state. See the NYNHP Rare animal list  for the listing of New York’s rare moths.

Quiz: What moth does this caterpillar become?

Woolly bear
The woolly bear caterpillar is the young phase of what moth? Answer at bottom of page. Photo by M. Schlesinger, NYNHP

For More Information:

Fun for all ages Moth Week  

Peterson First Guide to Caterpillars by Amy Bartlett Wright, 1983 (includes moths and butterflies).

A field guide to the moths of eastern North America by C. V. Covell, 2005.

Peterson first guide to butterflies and moths: a simplified guide to the common butterflies and moths of North America. P.A. Opler, 1994.

Butterflies and Moths of North America

New York Natural Heritage Program, Animal Guides

Butterflies and Moths, BugGuide

State Parks Moth Week Events

Quiz answer: The woolly bear caterpillar (Pyrrharctia isabella) becomes the Isabella tiger moth (Pyrrharctia isabella). Moths are one of the few groups that have different names for different life stages of the same animal. This is one reason why scientific names are important; from the common names we might think this caterpillar and moth were not related.

Isabella Tiger Moth
Isabella tiger moth, Fyn Kynd, 2015, accessed from BugGuide, http://bugguide.net/node/view/1162577

Post by Julie Lundgren, NY Natural Heritage Program

The Folklore of the Woolly Bear

Finding a banded woolly bear caterpillar during a walk in the woods leaves no doubt that autumn is upon us.  These familiar black and reddish-brown caterpillars are larval Isabella moths.

The woolly bears that we see in the fall are the second generation of woolly bears for the year; the first generation hatched out in May.  This second generation of woolly bears emerged back in August.  Since then , they have eaten leaves from a variety of plants from grasses to clover to trees and sunflowers.  Once the cold weather hits, the woolly bear finds a sheltered spot like rotted log, or under a rock, or in a pile of leaves, to overwinter. When the temperatures drop below freezing, woolly bears also freeze.  Fortunately woolly bears have a cryoprotectant, a natural sugar-based antifreeze which protects the caterpillar’s tissues from being damaged when it freezes.  In spring, woolly bears emerge from their sheltered spot, eat a few more leaves then make their cocoons and undergo metamorphosis to become an Isabella moth.

Moth
By Andy Reago & Chrissy McClarren [CC BY 2.0 (http://creativecommons.org/licenses/by/2.0)%5D, via Wikimedia Commons.
Folklore has it that woolly bears predict the severity of the upcoming winter based on the proportion of black and reddish brown banding on the caterpillar’s body.  A thin reddish brown band means we are in for a tough winter.

But is this folklore true?  Dr. C. H. Curran, curator of insects at the American Museum of Natural History in New York City (1928-1960) traveled to Bear Mountain State Park in 1948 to find out.  On a single day, he gathered as many woolly bears as he could find, compared the reddish brown segment to the black segment, then reported his findings and a winter weather prediction to a reporter at the New York Herald Tribune.  Dr. Curran continued his study for eight more years and was never able to conclude whether the woolly bear was able to predict the winter.

More recently scientists have found that the size of the reddish-brown band increases as caterpillar matures and that wet weather increases the size of the black bands.

While woolly bears may not be an accurate forecaster of the upcoming winter, they are still a delight to see during a visit to a park.  Perhaps you’ll see one curled in a ball or looking for the next leaf to eat.

Post by Susan Carver, OPRHP.