Howdy, BugFans,
The star of today’s show is the Virginian Tiger Moth (probably), not to be confused with the considerably-more-decorative Virgin Tiger Moth (Grammia virgo).
Tiger moths are in a tribe called Arctiini (Tiger moths) in a subfamily called Arctiinae (Tiger and Lichen moths) (formerly its own family), in the family Erebidae. Arctia comes from a Greek word meaning “bear,” a reference to the fuzzy Tiger moth caterpillars, many of which are called wooly bears: (Wooly Bears Bug of the Week Archive). There are more than 11,000 diverse species in the subfamily, and all have, on their metathorax (the third/back segment of the thorax) a tymbal organ – an organ that produces ultrasonic sound via vibrations. Because they make sound, it makes sense that they also have tympanal organs that allow them to hear it. They generate sound in courtship and for defense, including using vibrations to confuse bat echolocation.
The larvae of many Arctiinae are avoided by predators because the larvae feed on plants that produce noxious/distasteful chemicals (in order, of course, to avoid being fed upon), but caterpillars of some species can produce their own chemicals independently. Wikipedia says that they “may retain them in the adult stage, but adults can acquire them, too, by regurgitating decomposing plants containing the compounds and sucking up the fluid. Adults can transfer the defenses to their eggs, and males sometimes transfer them to females to help with defense of the eggs.”
And while many are drab, other species in the tribe Arctiini make us rethink our preconceptions about little gray moths:
- Haploa Sp.
- Tyria jacobaeae
- Faithful Beauty – Composia fidelissima
- Faithful Beauty – Composia fidelissima (caterpillar)
- Moth – Bertholdia trigona
- Pennsylvania Moth – Hypercompe scribonia
- Lerina incarnata
- Pseudosphex leovazquezae
VIRGINIAN/VIRGINIA TIGER MOTHS (Spilosoma virginica) are one of the species that have different names in different life stages – their caterpillars are called Yellow Woolybears and Yellow Bears. With the exception of just a few western Great Plains states, they’re found across North America from coast to coast and from northern Canada to the Rio Grande. Like many other Tiger moths, they are successful because their caterpillars are catholic in their food choices, which means that they might be seen in gardens, yards, roadways, woodlands, and fields, wherever their food/host plants grow.
They eat many kinds of plants, both woody and herbaceous, that grow low to the ground – grasses, clovers, milkweed, dandelion, plantain, honeysuckle, cherry, and some agricultural crops. Adults sip nectar.
No, they’re not flashy, but an inch-long Virginian Tiger moth with its 1 ½” wingspan is a perfect fluffy, snow white teddy bear of the Tiger moth family. Snow white except for its colorful front femurs, its black-wrapped tibiae and tarsi (“lower legs” and “feet”), and the gaudy decorations on its abdomen, beneath its wings, which it displays when it’s alarmed.
The caterpillars, which can be found from spring through fall, vary in color from cream to rust (which some suggest may be a function of age), and they’re covered with soft hairs – some exceedingly long – that are not venomous but that may affect sensitive individuals. Female caterpillars and moths are a bit bigger than their male counterparts.
When a young moth’s fancy turns to love, she releases a pheromone that the male tracks using his feathery, sensory antennae. Females lay eggs in groups of 20 to 100 on the undersides of a host plant’s leaves, and the newly-hatched caterpillars skeletonize leaves together for a while before going their separate ways. There are two generations each year, and although most sources say that the fall generation overwinters as larvae, emerges in spring to feed briefly, and then completes its metamorphosis; one source, the very-knowledgeable David L. Wagner, states in Caterpillars of Eastern North America that they overwinter as pupae.
[Caveat emptor. The UWM Field Station website is the home of the ‘Bug of the Week’ archives (thanks again, folks!). A few years ago, the BugLady included a brief account of the Yellow Woolybear caterpillar in an End of Summer wrap-up episode. When she began her recent Virginian Tiger moth research, this AI response/overview popped up: “The UWM Field Station (located in Saukville, WI) features extensive records and research on the Virginian Tiger Moth (Spilosoma virginica), a common white tiger moth whose larval stage is widely known as the yellow woolly bear caterpillar.” It doesn’t.]
The BugLady