Don’t Bug Me Now

The winter solstice—the shortest day of the year and the official start of winter—has come and gone, and the days are now getting longer.

In this cold, dormant time, it might come as a surprise to learn that insects survive the winter. They have various strategies to do this. Many species go through diapause, a delay in development in response to adverse environmental conditions. The eastern population of the Monarch (Danaus plexippus) butterfly migrated last fall to overwintering sites in the Oyamel Fir (Abies religiosa) forests of Mexico. They usually arrive there around the Día de las Muertos, which is celebrated November 1 and 2. They rest there and won’t feed on milkweed until temperatures are warmer. Then they begin to migrate back north. And the reason you can find the Mourning Cloak (Nymphalis antiopa) butterfly flying around so early in the spring (often in March in Connecticut!) is because in winter they hibernate as adults in tree holes and other crevices.

Mourning Cloak butterflies can be active in late winter and early spring because they have overwintered as adults in tree holes and crevices. This butterfly is using the heat from the dark rock to warm up. Photo by Ryan Hodnett, CC BY-SA 4.0 <https://creativecommons.org/licenses/by-sa/4.0&gt;, via Wikimedia Commons.

Many lady bugs, or ladybird beetles (family Coccinellidae), will overwinter as adults, piling on one another in big groups inside hollow logs and under rocks. This helps them stay hydrated and avoid predators. Last fall you might have noticed their large gatherings around your dark shutters and white-framed windows. Usually this is an introduced species, the Asian Lady Beetle (Harmonia axyridis). These beetles will sometimes crawl into a home through cracks. When disturbed, they emit an acrid odor and can stain surfaces with a yellow secretion.

This cluster of Asian Lady Beetles gathered together in a South Dakota farm building. Photo by Jared Birk, CC BY-SA 3.0 <https://creativecommons.org/licenses/by-sa/3.0&gt;, via Wikimedia Commons.

If you see a moth flying at night in December in Connecticut, it is likely the male Winter Moth (Operophtera brumata). This invasive species, introduced from Europe, can defoliate oak and maple trees as a caterpillar (larva). The larvae burrow into the ground to pupate and the adults emerge in late fall and early winter. In cold temperatures male moths rapidly vibrate their flight muscles to warm themselves and then fly off to seek out females. Females don’t fly, but crawl up a tree and emit a pheromone to attract males.

It’s strange to see a moth flying around in the winter, as this Winter Moth does. This invasive species can cause damage to native trees such as oaks and maples. Photo by Ben Sale from UK, CC BY 2.0 https://creativecommons.org/licenses/by/2.0, via Wikimedia Commons.

Some insects overwinter as larvae. The Wooly Bear caterpillar, the larva of the Isabella Tiger Moth (Pyrrharctia isabella), are seen traveling across roads and paths in the fall. They are now dormant under the heavy cover of leaf litter. These caterpillars produce glycerol, an antifreeze, which keeps their cells from freezing.

A Luna Moth spends the winter as a pupa or cocoon. In the fall, the larva will wrap leaves around itself with silk and then change into a pupa. If the leaves containing the cocoon fall to the ground before the adult emerges in the spring, it will spend the winter hidden in leaf litter. Photo by Carlowenby, CC BY-SA 4.0 <https://creativecommons.org/licenses/by-sa/4.0&gt;, via Wikimedia Commons.

Insect species that spend the winter as an egg include praying mantids. Before she dies in the fall, an adult female mantid will lay an inch-long (2.54 centimeters) frothy sac, which hardens into a protective egg case, or ootheca. I once made the mistake of bringing an egg case indoors one fall and that winter 100 young hatched!

A Praying Mantid ooetheca or egg case. Photo by Dhrm77, CC BY-SA 4.0 <https://creativecommons.org/licenses/by-sa/4.0&gt;, via Wikimedia Commons.

We might not be thinking of insects and other invertebrates as active now. But many of them are. Beneath the ice of ponds and streams the immature stages of stoneflies (order Plecoptera), caddisflies (order Trichoptera), mayflies (order Ephemeroptera), and dragonflies (order Odonata) are actively feeding on smaller aquatic invertebrates or plant material, depending on the species. These insects are growing and adding body mass so they can emerge as fully flighted adults in the spring. Dragonfly nymphs, like the adults, are carnivorous, feeding on other invertebrates and even tadpoles and salamander larvae. Some spend a few years as a nymph before maturing into an adult.

Dragonfly nymphs are one of many aquatic macroinvertebrates active during the winter. The nymphs are one of the top aquatic predators for their size. Photo by Judy Gallagher, CC BY 2.0 <https://creativecommons.org/licenses/by/2.0&gt;, via Wikimedia Commons.

The larvae of caddisflies are found in a wide variety of aquatic habitats, including streams, rivers, lakes, ponds, and vernal pools. Many species of caddisfly larvae use silk to make protective outer cases with gravel, sand, twigs, bitten-off pieces of plants, or other debris. The larvae feed in different ways depending on the species. Some are predators, some shred leaves, others graze on algae or collect particles from the water column or on the bottom.

We don’t often think about insects during the winter, or just believe that most have died. If we do see one, we think it is an anomaly or accident of nature. In fact, many insects are still living with us, either dormant or active, during the winter months.

Published by Jim Sirch

Jim Sirch is the author of Beyond Your Back Door, a weekly blog about nature in your neighborhood. He is also Education Coordinator for the Yale Peabody Museum, a UConn Master Gardener and board member of his local land trust. As a trained naturalist, he brings a deep understanding of geology, plants and wildlife and how they interact within a particular ecosystem. He holds a B.S in Forestry from West Virginia University, a B.S. from Miami University in Science Education; and an M.S. in Environmental Studies Administration from Antioch University. He is also the 2014 Sigmund Abeles Award recipient from the Connecticut Science Teachers and Supervisors Association for outstanding science teaching and professional development.

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