Gardening Tips: October 29, 2013
Besides being a great year for all sorts of wild foods, I have noticed that it is also a banner year for wooly bear caterpillars. I see them every day, crossing the roads and in my driveway, my woodpile and just about everywhere else.
These furry creatures are scientifically known as the Isabella Tiger Moth (Pyrrharctia isabella). This insect is common in many cold regions and is well known to adults and children of all ages. It looks like something that would crawl off a teddy bear with its fuzzy brown and black bands. It has black fur on both ends and a reddish, brown band in the middle of its body.
Unlike most caterpillars that we are familiar with, the wooly bear hatches from eggs in the fall and spends the winter as a caterpillar. Most of our well known Lepidopteran larvae (caterpillars that turn into butterflies or moths) such as gypsy moths or forest tent caterpillars, hatch in the spring, pupate in mid-summer, emerge as moths after metamorphosis in their cocoon. They then mate and lay their eggs. The eggs overwinter to complete the life cycle. Wooly bears behave very differently. In very cold climates, such as the arctic, Wooly bear caterpillars may spend several summers feeding before they finally pupate. It has been reported that some wooly bear caterpillars have gone as long as 14 years before they pupate.
One might think that these caterpillars would freeze during our cold NY winters. In fact, they do freeze. First, its heart stops beating, then its gut freezes, then its blood, followed by the rest of the body. It survives being frozen by producing a cryoprotectant in its tissues. A cryoprotectant is a substance that is used to protect living tissue from freezing damage (i.e. that due to ice formation). Arctic and Antarctic insects, fish and amphibians create cryoprotectants (antifreeze compounds and antifreeze proteins) in their bodies to minimize freezing damage during cold winter periods. Insects most often use sugars or polyols as cryoprotectants. Cryoprotectants operate simply by increasing the solute concentration in cells. However, in order to be biologically viable they must (1) easily penetrate cells, and (2) not be toxic to the cell. In the spring it thaws out and emerges to pupate. Once it emerges from its pupa as a moth it has only days to find a mate.
Wooly bears have a good deal of folklore associated with them. It has been said in the eastern United States and Canada that the relative amounts of brown and black on the skin of a Woolly Bear caterpillar are an indication of the severity of the coming winter. It is believed that if a Woolly Bear caterpillar’s brown stripe, in the middle of its body, is thick, the winter weather will be mild and if the brown stripe is narrow, the winter will be severe.
Not much alike
In reality, hatchlings from the same clutch of eggs can display considerable variation in their color distribution, and the brown band tends to grow with age; if there is any truth to the tale, it is highly speculative. I have seen dozens of wooly bears this fall and some have wide stripes while others have narrow brown bands.
Bald-faced hornet nests have also been speculated to predict the severity of the upcoming winter. It is said that the higher above the ground the nest is constructed, the worse the winter will be. This summer I have observed these grey colored, paper like nests, both high up in a tree and also just above the ground in a bush.
The sad fact is that no one has a clue as to what the upcoming winter will be like. Meteorologists are pretty good at predicting weather a few days in advance but their track record is not great beyond that. My prediction never varies. It will be cold and it will snow and I will be in Florida for most of it!