Hardy insects winter here
While it will be a few months before the early flowers start poking their happy little faces through the snow, warm days are already awakening a few flower bulbs down on the Front Range.
I understand they’re using their stored reserves to get a jump on the sunlight to get their life cycle out of the way before any of the bigger competition awakens from its winter slumber.
Still the sight of crocuses and daffodils resolutely piercing the hard crust of snow and opening into bright daubs of color, refreshing the tired monochrome of winter, always amazes me.
Then I get to wonder about the flowers. A flower’s job is to attract insects for pollination services.
What and how are insects buzzing around in the middle of winter? I know one kind at least. Recently, a butterfly fluttering across a sunny meadow hypnotized me.
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Two kinds of butterfly over-winter in the Rocky Mountains – the mourning cloak and Milbert’s tortoiseshell.
The mourning cloak is perhaps the world’s longest-living butterfly, with a lifespan of 10 months. Both creep into sheltered crevices in bark, leaf litter, caves and emerge in spring to mate. Both can also wake up on a warm day, absorb the sun’s heat and go for a midwinter romp, sucking down tree sap for nourishment before hibernating again.
Butterflies are apparently sturdier than the gossamer fragile image they present and better fliers than I’d assumed merely on their apparently uncontrolled haphazard flight. A lepidopterist told me they’re not haphazard at all, and they go exactly where they want to with incredible precision. They’re following scents, which are haphazardly scattered in the air’s turbulence.
On days over 60 degrees you can see either. Milbert’s tortoiseshell has a bright orange band, and the mourning cloak is dressed in a respectful shimmer of brown-purple wings trimmed with an ivory band. Perfect funeral colors.
How can insects survive these cold winters and be ready when the spring flowers arrive? We marvel at large furry mammals and their ability to hibernate, but bugs are just bugs. Insects survive by going into a state called diapause, one of arrested development in which growth and any metamorphosis stops. Some can survive temperatures of minus-94. Insects have the advantage of different life stages to choose for their diapause. A larval stage that isn’t a feeding stage is a good strategy (pupae, eggs).
Alpine insects are divided into two camps. They’re either freeze-susceptible or freeze-tolerant. Freeze-susceptible avoids freezing by making glycerol or ethylene glycol. Beetles invented antifreeze long before we did. Freeze-tolerant insects survive by freezing.
The key here is to avoid any water freezing inside the cells where ice crystals will rupture vital lipid membranes and kill the cell. Instead the insect induces freezing in the gut cavity, the blood and in the spaces between the cells. This freezing draws water from the cells, making the small amounts left hard to freeze.
Thawing and refreezing with temperature fluctuations are a pain. Most choose a sheltered spot that will maintain a constant temperature for their cryogenics.
Size matters. The smaller the animal, the easier it can super cool without freezing. Ants have an easier time than beetles, and this applies within species, too. A big fat fly will suffer more than a little relative.
When active, flies are very useful pollinators for alpine plants, since they can fly at low temperatures and need little fuel. Bees need to get their thorax up to 85 degrees before they can fly, but they can “shiver” (muscular thermogenesis) to do this. This ability to shiver allows bees to be active when other nectar feeders can’t, a large advantage.
Butterflies need to bask in the sun until they heat up to 80 degrees.
While I enjoy the spring flowers for themselves and as a metaphorical sign for the loosening of winter’s frozen handshake on my life, this is literally the case for the insects that have avoided dying to visit those flowers. The closer you look at nature, the more marvelous it and the blind watchmaker of evolution become.
Alan Braunholtz of Vail writes a weekly column for the Daily.