The Virginian Tiger Moth: Spilosoma Virginica

The Identity Crisis of Spilosoma Virginica, the Yellow Bear Caterpillar or Virginia Tiger Moth
By Steve Carbol, Lake & Wetland Management Senior Biologist

The Yellow Bear Caterpillar Known as the Virginian Tiger Moth

As humans, we feel a deep-seated need to name things because it helps us identify, understand, categorize and communicate about the things around us. Unfortunately, the names with which we saddle wildlife are often confusing and only apply to a particular gender, population, or life stage. Such is the case with the Virginia Tiger Moth.

What’s in a Name?

fuzzy caterpillar crawling along a twigMany tiger moths live up to their name and are ornately patterned like their feline namesakes, but not the Virginia Tiger Moth. As adults, Virginia Tiger Moths are strikingly but simply clad in bright white dotted here and there with a few small black spots. They also hide tangerine blazes on their abdomens and under their chins. And while the Virginia Tiger Moth does indeed occur in the Old Dominion State, it is a wide-ranging species found across much of the lower 48 United States and southern Canada, south into Central America, so “Virginia” too does little as a descriptor.

Virginia Tiger Moths vs Tiger Moths

Some tiger moths, but not the Virginia Tiger Moth, are ornately patterned like their feline namesakes. As adults, Virginia Tiger Moths are strikingly but simply clad in bright white dotted here and there with a few small black spots. They also hide tangerine blazes on their abdomens and under their chins. And while the Virginia Tiger Moth does indeed occur in the Old Dominion State, it is a wide-ranging species found across much of the continent, so “Virginia” does little as a descriptor.

You Got The Look

To muddle things further, because the young are caterpillars, they’re technically not yet moths and are instead known by other monikers such as “Yellow Bears” or “Yellow Woolly Bears”, not because they look anything like bears, but simply because they’re fuzzy wuzzy, and if we all remember our schoolyard rhymes, Fuzzy Wuzzy was indeed a bear, but wasn’t very fuzzy, wuz he? If this isn’t already sufficiently baffling, the larvae look confusingly similar to caterpillars of several other related species, and though they often occur in yellow, individuals don’t always necessarily live up to that name either.

Yellow Bear caterpillars wear a bristly protective coat of setae (hairs) and come in an assortment of solid colors the envy of any hair colorist including platinum blonde, sandy brown, cinnamon orange, auburn, chestnut, and mostly black. Really, who named these things?

The Caterpillar Life Stage of the Virginian Moth

Yellow Bear caterpillars wear a bristly coat of setae (hairs) and come in an assortment of solid colors the envy of any hair colorist, including platinum blonde, sandy brown, cinnamon orange, auburn, chestnut and mostly black. The setae or bristles can be irritating to some people if they are picked up. The caterpillar’s body has thirteen segments. They can molt as many as six times during their caterpillar stage.

There are generally two generations of caterpillars each year, one in May and one in August. When the woolly bear caterpillar has eaten enough food, it will form a chrysalis or cocoon and emerge in three to four weeks as a moth.

fuzzy black caterpillar crawling on a leaf

Are Yellow Woolly Bear Caterpillars Poisonous?

Though called the Woolly Bear because its bristles look like wool, it does not feel like wool at all, instead, it feels spikey. They do not cause disease, but for people with sensitive skin, these spikes can be an irritant, causing itching and dermatitis. This may have led some people to think they are poisonous, however, they do not inject any venom.

Diet of the Virginian Tiger Moth

Perhaps taking a cue from their exceptionally variable looks, both larvae and adults are generalists and quite catholic in their taste in food plants. The caterpillars aren’t picky and consume the leaves of hundreds of species of grasses, herbs, and trees, with some showing a distinct preference for legumes.

An All-Inclusive Menu

The nocturnal adult moths unfurl a long proboscis to sip nectar at a wide variety of flowers including asters, goldenrods, daisy fleabane, Plucheas, mints, thistles, and butterfly bush (Buddleia). This dietary flexibility undoubtedly contributes to the species’ wide range, commonness, and adaptability.

Male Virginia Tiger Moths vs Female Tiger Virginia Moths

Male Virginia Tiger Moths are slightly smaller than their female counterparts and exhibit broader, more feathery antennae used to detect the females’ alluring airborne pheromones. Following a romantic encounter, the females seek out one of the species’ many host food plants and lay 20-100 pinhead-sized, translucent, chartreuse, spherical eggs.

The Circle of Life

After hatching, the tiny larvae gorge on leaves day and night, shedding their skin periodically as they grow at an exponential rate. The caterpillars become much more obvious in the winter months as many approach later instars and grow larger and more visible, at lengths of an inch or more.

Upon eating their way to maximum size, the Yellow Bear caterpillars construct and attach to a structure a cocoon of silk and their own irritating setae hairs to deter predators while they ride out the cooler winter months and pupate inside to emerge in Spring as adult Virginia Tiger Moths.

Habitat of the Virginia Tiger Moth

Though we might have some uncertainty over the myriad aliases and changing the appearance of this species, these insects show no confusion themselves as they self-possessedly go about their lives, flying, marching, and munching through our local wetlands, grasslands and woodlands. With its conspicuous coloration, approachability, fuzzy cuteness, and engaging ongoing lifecycle saga of eating, metamorphosis, and reproduction, the Yellow Bear/Virginia Tiger Moth is yet another interesting member of Florida’s extensive list of watchable wildlife. I suppose the moral of the story is that regardless of what names others call you, it’s most important to be yourself.