Bug of the Month Wooly Bear Caterpillar

As far as the story about the woolly caterpillar’s coat, this is how Mother Nature helps it survive winter.  The fur is called setae and it isn’t there to protect them from the cold weather.  Instead, it actually helps them to freeze more controllably.  Here is something truly remarkable.  Once settled in, the caterpillars hibernate, creating a natural organic antifreeze called glycerol.  They freeze bit by bit, until everything but the interior of their cells are frozen.  These interior cells are protected by the hemolymph.  Woolly bears can – and do – survive to temperatures as low as -90oF.  This ability to adapt to cold shows up particularly in the Arctic, where the woolly worms live in a strange state of slow motion.  Most caterpillars live for two to four weeks before becoming moths.  The Arctic woolly worms, however, spend at least 14 years in the process!  The woolly bear caterpillar has even been known to survive an entire winter completely frozen in an ice cube.

As winter approaches, the worms stop feeding and empty their digestive and excretory systems by defecating — pooping — out any contents. That ensures they “get rid of anything that could cause ice crystals to form,”. An insect “antifreeze” made of sugars, proteins and alcohol, is produced by the insects internally and circulates in their blood, helping woolly bears survive temperatures far below zero degrees.

Once warmer weather returns, the antifreeze breaks down and the caterpillars begin moving again.

Yet another name for this caterpillar is the Hedgehog Caterpillar, because it curls into a tight bristly ball and “plays dead” when picked up or disturbed.  Whatever name they go by, they are often found in the autumn after they have left their food plants (variety of grasses and weeds including plantain, dandelion, and nettles) in search of a dark and sheltered spot where they can hibernate as larvae for the winter.

 Outsmarting predators: The woolly bear’s stiff hairs are an important defense against predators such as yellow jackets and other wasps. By curling into a ball, caterpillars position their bristles on the outside and protect vulnerable organs.

“The wasp has to be really hungry to want to tackle a bristly caterpillar,”.

Some species have developed defenses against parasites, which attack from inside caterpillars’ bodies. Normally woolly bears avoid eating plants with bitter compounds, called pyrrolizidine alkaloids, because they can stunt growth. But scientists found that when flies laid eggs on caterpillars and the larvae started feeding on them, the caterpillars began to “self-medicate” by eating plants with bitter compounds. Entomologists are studying how this behavior helps the caterpillars but suspect it makes them unpalatable to the parasites.

Woolly Bear Folklore:

The longer the woolly bear’s black bands, the longer, colder, snowier, and more severe the winter will be. Similarly, the wider the middle brown band is associated with a milder upcoming winter