Sunday, November 16, 2014

Lawns, Tiger Moths, and Woolly Bears, Oh My...

     Tiger Moths are a fascinating group of moths in the subfamily Arctiinae (formerly family Arctiidae). They are better known from their larva, the normally hairy caterpillars with the typical "woolly bear" look that we often see crossing our lawns and driveways. The hairs on the caterpillars easily come off and are uncomfortable for many animals' throats, giving them some measure of protection. Most of the caterpillars themselves are distasteful to many potential predators as well.
     They are most commonly seen while wandering about in Fall when many species are looking for places to overwinter. Many of them spend the winter in caterpillar form, under a log or otherwise hidden. They awaken the following spring and continue feeding as caterpillars for a while before pupating and emerging as tiger moths in the summer.

The Woolly Bear caterpillar, the larva of the Isabella Moth and predictor of winter weather.

     The best known and typical member of the family is the Woolly Bear or Woolly Worm, black on both ends and reddish brown in the middle. Because it curls up into a bristly ball when it is in danger, it is also sometimes called the Hedgehog Caterpillar. This is the larva of the Isabella Moth (Pyrrharcttia isabella) and folklore claims that by looking at the amount of black on its body, the severity of the winter can be forecast. The longer the black bands, the colder the winter, while the longer the brown band, the milder. The color differences are more likely due to what the larvae experienced in the past rather than what will occur in the future. They are commonly seen crossing roads, lawns, and driveways in the Fall and sometimes even on warm winter days. 
    There are several other species of woolly bear-type caterpillars in this group, only a couple of which are shown here. Most feed on a variety of low to the ground plants, overwinter as larvae, and then complete their metamorphosis the following summer, but there are several exceptions.

The Northern (Giant) Leopard Moth caterpillar, not only larger than the typical woolly bear, but also has red segments in between black bristles.

They Yellow Bear, the caterpillar of the Virginian Tiger Moth, is very variable, ranging from yellow to almost red, but always with hairs on its body of different lengths.

The Delicate Cycnia or Dogbane Tiger Moth caterpillar is usually more visible in summer, light colored on dogbane or milkweeds.

Fall Webworm Moth caterpillars are usually noticed in their web nests, but wander off to pupate.

The Agreeable Tiger Moth can be a bit variable, but is a fast moving caterpillar, often with hairless segments. 

     The adult tiger moths tend be bright colored, often white, as warning colors at night. Several of the fuzzy moths are poisonous to many potential predators. They not only announce this by their coloration, but have another means of doing so. When a tiger moth hears a bat coming after them and using its echolocation to find them, they not only take evasive action like most moths, but also vocalize back.

Delicate Cycnia or Dogbane Tiger Moth, showing the typical white coloration of the family. 

     The sounds they send out originally were believed to "jam" the bat's echolocation, but now it appears that they are actually warning sounds. They warn the bats that the tiger moths are distasteful. If they eat one, they will there after link the sound the tiger moths make with how bad they taste.

An Agreeable Tiger Moth - most tiger moths are white or light colored; the only warning colors that show up at night.
The Clymene Haploa is sometimes called the Upside-Down Cross Moth.

     This group of hairy caterpillars and the tiger moths they turn into are interesting and luckily fairly common. People of all ages always seem to be amused and curious when they discover them. Now perhaps we can appreciate them even more knowing more about them.


  1. My daughter always likes to pick up furry caterpillars. Do any of them have poisonous, needle-like bristles, or are they all just soft and furry and safe to touch?

    1. If you're not sure which caterpillar you've encountered, it's best to leave them be, just in case. But the ones mentioned here do not.