Wondering on woolly bears in winter (kinda solving the mystery)
Frank Chesniak wondered whether the woolly bear caterpillars he saw in his woodpile Sunday were dead.
‘‘The woolly bear caterpillar (or, more precisely, the Isabella tiger moth) is a great example of insect strategies for cold and has become fairly well-known in the literature,’’ emailed Derek Rosenberger, an associate professor in Wheaton College’s Conservation and Ecological Health Program, who worked with mountain pine beetles and researched cold tolerance.
‘‘Most insects in temperate regions will develop cold tolerance to some degree through the fall as cryoprotectants develop in their bodies. Cryoprotectant compounds allow the insects to lower the point at which ice will form in their bodies, which is good! The mountain pine beetle for instance . . . could survive temperatures down to -22 degrees Fahrenheit!
‘‘However, despite lowering the freezing temperature of their body fluids, some insects still die prior to freezing, and some can actually survive their bodies freezing! Insects that survive freezing are called freeze-tolerant insects. The woolly bear falls into this special category. Temperatures need to go below around 15 degrees Fahrenheit for the caterpillar to freeze, but even then, after thawing, it can survive. In our region, however, the caterpillar might need to rely upon this strategy multiple times, which can be costly to the insect, as a paper out of Brent Sinclair’s lab has shown, with each freezing event reducing its likelihood to survive.’’
Here is an extended explanation from Rosenberger:
So, what woolly bear caterpillars may do is seek out a place that might be buffered against temperature fluctuations. The subnivean environment below snow is a great place, as the temperature stays fairly consistent. Other places might be under leaf litter or in wood piles, which is where your reader found their specimen waiting out the winter.
Being able to survive freezing, rather than lowering your freezing point so that freezing doesn’t occur, is a really neat but not so common overwintering strategy, so this critter has gotten quite a bit of attention in the insect cold tolerance circles.
Rosenberger linked to this: The sub-lethal effects of repeated freezing in the woolly bear caterpillar Pyrrharctia isabella | Journal of Experimental Biology | The Company of Biologists
Wild things
Multiple readers have reported dead waterfowl from suspected avian flu and wonder what to do. Start with this on the protocols from the Illinois Department of Natural Resources: dnr.illinois.gov/press-release.30768.html.
Stray cast
Bears fans are like largemouth bass with multiple old hook marks.