A Bug’s Winter
Left photo: A Woolly Bear caterpillar survives winter in a kind of hibernation called diapause, hidden under leaf litter. Photo by Kristina Swerhun Right photo: A Woolly Bear caterpillar survives winter in diapause, hidden under leaf litter, before transforming into an Isabella Tiger Moth. Photo by Chloe Van Loon
Have you ever wondered how insects survive the winter? Unlike humans, they can’t regulate their body temperature, so they have evolved incredible adaptations to survive the cold. Though these adaptations vary widely, here are some ways insects survive winter in Whistler.
Migration: Though not common, examples from Whistler include the Painted Lady butterfly and the Common Green Darner dragonfly, both of which rely on multiple generations to complete their cycle to and from warmer regions in the south.
Diapause: This period of suspended development, much like hibernation, is common and triggered by shorter days and cooler autumn temperatures. Depending on the insect, it may pause as an egg, larva, pupa, or adult. To survive freezing temperatures, insects produce glycerol—a natural antifreeze that prevents cell-damaging ice crystals from forming. This lets them freeze and thaw multiple times without harming their internal organs.
An insect that enters diapause as a larva is the Woolly Bear, a fuzzy black-and-rust-banded caterpillar that is the larva of the Isabella Tiger Moth. It spends the winter hidden under leaf litter, under logs, and in garden debris piles. You might see these caterpillars out looking for shelter in the fall, or on mild winter days when they occasionally walk around.
The Western Tiger Swallowtail—a large, bright yellow butterfly with black stripes (like a tiger) and hindwings shaped like some swallow’s tail feathers—enters diapause in its pupa stage as a chrysalis. You can find its chrysalis in winter attached to trees or in protected shrubs. Look for adults pollinating sturdy flowers or drinking muddy, mineral-rich water on the ground.
While most butterflies diapause as eggs, larvae or pupae, the Mourning Cloak pauses as an adult. This butterfly is red-brown with a thick yellow border along the edge. It finds shelter beneath tree bark, or anywhere it can fit, to protect itself from winter wind and to hide from predators. They are among the hairiest butterflies, which keeps them insulated and able to fly in cooler temperatures. That is why they are usually the first butterflies we see in the spring.
Adult Lady Beetles (Ladybugs) are another example of pausing as an adult. They live for about three years and spend winters in large groups in leaf litter. Lady Beetles are extremely helpful insects as they keep populations of aphids and other perceived pests to a minimum.
Diapause – aquatic edition: Many people are surprised to learn that dragonflies spend most of their lives underwater, and that at least 32 different species are found in Whistler. They don’t have a complete metamorphosis like butterflies and Lady Beetles do, but go from egg to larva (nymph) to adult, without a pupal stage. Dragonflies can spend as much as five years underwater, while their adult stage on land usually only lasts a few weeks. During winter, some dragonfly nymphs continue to crawl and feed slowly beneath the ice or enter diapause to save energy until spring.
If you want to do your part to help insects survive, remember not to clean up around the yard too heavily in the fall. This extra layer of insulation could make all the difference for a healthy insect ecosystem.
Written by: Kristina Swerhun
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