The Carlisle Mosquito Online

Friday, November 12, 2010


Yellow Bear caterpillar

Tiger Moth caterpillars are hairy creatures. They are members of the sub-family Arctiinae, a name derived from the Greek word “arctos” meaning bear. The best known caterpillar of the group is the black and brown Wooly Bear. Today’s topic is the Yellow Bear, Spilosoma virginica.

The Yellow Bear now. (Photo by Kay Fairweather)

Name: Some moths have different common names for the caterpillar stage of the life cycle and the adult stage. The Yellow Bear is an example. It metamorphoses into a moth called the Virginian Tiger Moth (not to be confused with the Virgin Tiger Moth which is a horse of another color). Moths with only one common name, regardless of the stage in the life cycle, may be named for characteristics of either the caterpillar or the adult moth. An example from the same sub-family as the Yellow Bear is the Giant Leopard Moth. Its caterpillar has no spots and looks nothing like a leopard but has no name other than that of its adult form which is prominently spotted. Conversely, the common name of some moth species is descriptive of the caterpillar. For example, there are the Loopers, Webworms, and the Hickory Horned Devil. Moth psychiatrists are grateful for the work we have created for them with these identity crises.

The Yellow Bear Moth as you will see it this summer.
(Photo by Kay Fairweather)

When and where found: I found this caterpillar on October 26 on a milkweed leaf in my yard. Yellow Bears can be seen up through November. They are not too picky about their food and will eat from many different low-growing plants, trees or shrubs. They pupate before the winter and emerge as moths in the spring. Their close relatives, the Woolly Bears, spend the winter as caterpillars and feed again in the spring before pupating. I sometimes find a Woolly Bear in the winter curled up deep in the wood pile.

Caterpillar characteristics: The Yellow Bear is not always yellow. Its color changes as it grows and molts. It starts out very pale yellow and darkens as it ages. This specimen was almost orange. It can be distinguished from other hairy caterpillars by the length, the softness, and the tufting of the hairs. Many of the other caterpillars have shorter and more bristly hair. The Yellow Bear would not make it in the military. It has never heard of a crew cut. Some of its hairs are much longer than the others. Often there is a single long hair, as long as three body segments, in each little tuft.

Moth characteristics: Yellow Bears turn into moths that are pure white with a few black dots. They are a brighter white than the drab white of the Cabbage White butterfly. They have a pure white hairy ‘mane’. The reason for calling the group “Tiger” moths is that some members have orange and black tiger-like markings.

References: Caterpillars of Eastern North America, David L. Wagner

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