If you move an outdoor flower pot, stick of firewood, or some similar item in the yard this winter, you may encounter a large, hairy black caterpillar curled up in some protective crevice beneath the item you moved. Giant leopard moth caterpillars, a.k.a. giant woollybears, overwinter as partly-grown larvae, and do not form cocoons and complete their development until spring. These caterpillars are well-adapted to survive freezing winter temperatures, and they occur throughout the US and into Canada. During the winter months they are able to produce antifreeze in their blood to protect them from freeze injury.
Interestingly, another member of this family, the Artic woollybear, must survive many annual cycles of freezing and thawing to complete their larval development. Artic summers are just too short for these caterpillars to do all their growing in one year; it takes about seven years for them to mature and pupate. Here in the South, giant leopard moth caterpillars can complete two generations per year, and it is only caterpillars of the second generation that overwinter.
Mature caterpillars are up to three inches long, and if you look past those stiff black hairs you may notice narrow red bands on the skin (not visible in this photo). The heavy-bodied adult moths are about two inches long and have white wings covered with circular black spots. This is why they are called leopard moths. Usually the spots look like thick black rings with white centers, but sometimes the spots are filled with black, or even blue, especially near the front part of the body, and the upper surface of the abdomen, which is visible only when the wings are extended, is covered with iridescent blue and orange markings.
Although these big caterpillars feed on a wide range of plants, including many ornamental and vegetable plants, they rarely occur in large enough numbers to cause serious damage or to make treatment necessary. Despite those stiff black hairs, these are not “stinging caterpillars.”
Like giant leopard moths and many other insects, the Bug’s Eye View Newsletter also becomes inactive during the winter months, but publication will resume next spring—about the time giant leopard moths resume their activity.
Blake Layton, Extension Entomology Specialist, Mississippi State University Extension Service.
The information given here is for educational purposes only. Always read and follow current label directions. Specific commercial products are mentioned as examples only and reference to specific products or trade names is made with the understanding that no discrimination is intended to other products that may also be suitable and appropriately labeled.