by Kate Redmond
Giant Leopard Moth
Howdy, BugFans,
Honorary BugFan Lisa sent the BugLady a picture of her glove posed next to a big, fat caterpillar and asked if it might be a wooly bear. There are a number of species of caterpillars that are called wooly bears, but the wooly bear in question is the caterpillar of the Isabella Tiger Moth, a caterpillar that has found a place in folklore for its (supposed) ability to predict winter weather https://uwm.edu/field-station/bug-of-the-week/wooly-bear-caterpillar-again/. When a wooly bear has wide, black bands, it’s predicting a harsh winter. Mistaking this black caterpillar for a wooly bear that’s gone all in for an Armageddon winter is a common mistake
Turns out that the caterpillar was something less common and way more exciting, and coincidentally, the BugLady had found a similar caterpillar in the same area earlier in fall. She’s seen one adult – tucked up under the eaves in Ohio, and would love to find another.
GIANT/GREAT LEOPARD MOTHS, aka Eyed Tiger Moths (Hypercompe scribonia) (also called “fever worms” in Missouri) are in the family Erebidae – Erebidae comes from the Greek Erebus, which means “from the darkness.” The family was created from parts of several other moth families, and it includes the Tiger https://www.bugguide.net/node/view/1548841/bgpage,
Lichen https://www.bugguide.net/node/view/2144967/bgimage,
Tussock https://www.bugguide.net/node/view/987864/bgpage, and
Underwing moths https://www.bugguide.net/node/view/2284502/bgimage, among others, whose subfamilies and tribes have some pretty spiffy members.
Look for Giant Leopard Moths in grasslands and along woodland edges from the Great Plains to the Atlantic and from far southern Ontario through Texas to South America. They are widespread but are not considered common within their range.
This is one spectacular moth! Some individuals are more “dotted” https://www.bugguide.net/node/view/1852552/bgimage than “eyed” https://www.bugguide.net/node/view/2265267/bgimage, and those beautiful, black and white wings hide a colorful body https://www.bugguide.net/node/view/977160/bgimage. And then there are the blue spots (more prominent in some individuals than in others) (and again – how does iridescence benefit a nocturnal species?) https://www.bugguide.net/node/view/1967173/bgimage! And they’re sizeable moths https://www.bugguide.net/node/view/2254472/bgimage, with a wingspread exceeding three inches (females are a bit larger than males https://www.bugguide.net/node/view/1388256/bgimage). There are six other members in the genus Hypercompe in North America, mostly western or Texan, and they all have a similar gestalt.
Ohio blogger Jim McCormac notes that, counterintuitively, this brilliant moth can be difficult to see on a tree trunk, its shape broken up by the pattern of dots and eyes. It has been theorized that the bold, black and white wings may be a kind of aposematic (warning) coloration because the moths do have a chemical defense – when alarmed, they exude drops of bad-tasting, yellow liquid from their thorax https://www.bugguide.net/node/view/1586453/bgimage. The moths will flip their wings up and display their technicolor body, possibly a behavioral defense to scare predators. Apparently, no one knows if they’re palatable to birds, and the BugLady didn’t find any accounts of enterprising scientists who admitted to tasting one (don’t laugh, someone tried a Viceroy butterfly) (not toxic like its Monarch look-a-like, but bitter because the caterpillar eats willow leaves).
Older caterpillars, which may grow to three inches long, have red spiracles (breathing pores) in a line along their sides, and red bands between the segments https://www.bugguide.net/node/view/58331. The BugLady once used the metaphor of a demure woman whose undergarments are red, but she may well have borrowed that phrase from somewhere. Some fuzzy caterpillars have irritating hairs, but not Giant Leopard Moths.
Adults mate, a process that may take as long as a day and include walking from sunny to shady spots as needed. Eggs are laid on one of the species’ many host plants, which include some woody plants (maples, willows, cherries, and mulberries), but mostly a variety of low-growing, bitter, herbaceous plants like dandelions, broad-leaved plantain, violets, and, surprisingly, broccoli and cabbage. Caterpillars are nocturnal eaters that hide under leaf litter or tree bark during the day. Adults do not feed.
They overwinter as caterpillars, often under the bark of decaying trees, fortified by a natural glycerol antifreeze. Jim Sogaard, in Moths and Caterpillars of the North Woods (a great little book that’s currently out-of-print, so snap one up if you find one) writes that “Caterpillars can survive temperatures of 26.6 degrees F. with 45% of their body water frozen to ice but perish when temperatures reach 14 degrees F.” Like the wooly bear, caterpillars may rouse during mid-winter thaws and take a hike, only to tuck themselves in again when winter returns. There’s one generation per year in the north and multiple generations in the south, where the final generation of caterpillars overwinters. They form a cocoon in spring.
Kate Redmond, The BugLady
Bug of the Week archives:
http://uwm.edu/field-station/category/bug-of-the-week/