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Where insects go in forest during winter

During winter months we hear few if any buzzing, bothersome gnats, mosquitoes or other airborne pests. Have no fear ... they are near.

From the tree canopy to the tree roots insects and many other invertebrates are in diapause waiting to emerge when days grow long and warm. They do so as adults, as pupae (larvae) or as eggs, sometimes in a completely frozen state. Unseen by us in the winter, there is an abundance of life hidden in our forest. From insect larvae growing in plant stems to frozen frogs beneath the forest floor they are there, just not in evidence. Dark green mistletoe can be seen clinging to barren limbs while beneath our feet soft green moss grows at a faster rate than it grows in summer. Of course, that in itself is not very fast. Moss attaches itself to surfaces by hook-like structures called rhizoids and among these structures many invertebrates can find enough warmth to sustain them during the cold months. Insects take refruge where they can and in manners that are suited to each species.

Some of our most well-loved and most recognized insects like the Monarch butterfly, the Gulf fritillary, and the Painted Lady butterfly actually get up and leave in winter. They migrate to warmer climates, but others hibernate.

Diapause is a long-term state of suspension which many beetles such as the emerald ash borer go into. They can be found in crevices of tree bark or nestled in roots. The two- and the 17-year cicadas live underground and emerge as nymphs when their winter bed begins to warm.

Some caterpillars, like the woolly bear create an antifreeze called cryoprotectant. This keeps their body from forming ice crystals allowing them to freeze and thaw several times over the winter. They can be found under leaf litter or just below the surface of the forest floor.

The Mourning Cloak butterfly reduces water and builds up glycerol to protect her soft body. She can be safe under rocks or crevices of tree bark.

Insects can also hibernate as adults. Ladybug beetles, brown marmorated stink bugs and ants sometimes find their way into warm man-made environments like your garage or underneath window sills. They “lay low” until spring then crawl out and become available for us to observe.

This is true also of the queens of the hornet and yellow jacket. The males die off before winter, but the fertilized queens burrow underground, go into diapause and wait to lay their eggs in spring.

The springtrail, a tiny black jumping nuisance, can be seen out on cold snowy days. This insect produces a protein that scientists have found they can manufacture to keep human tissue from freezing. This protein is used to extend the time harvested human organs can remain viable for transplant. (Purdue University, Brian Vallheimer Feb. 3, 2021)

Beware as you walk through the forest because ticks, also can be found under leaf litter and will come out on warmer winter days.

Honey bees, ants and termites may find a safe place above ground and produce their own warmth by an activity called huddling. The interior insects beat their wings (wing-fanning) to create heat and the outer insects create a protective wall to help maintain that heat. These workers continually change places just like geese flying in a “V” with the leader staying in the lead for a short time then changing places with others.

Luna moths, flies and some mosquitoes survive winter as pupae beneath leaf litter or underground. They can be camouflaged by wrapping themselves in leaves with soft webbing. The Luna Moth’s pupa is equipped with spurs on the forewings used to cut through the casing when the time is right to morph from pupa to adult. These spurs work like the alligator egg tooth found on the tip of the reptiles’ snout.

Some insects survive underwater. Nymphs of dragonflies, mayflies and stoneflies can wait out winter underwater living on stems of water plants. These nymphs are eating machines eating anything smaller than themselves and sometimes fish that are just a little larger than themselves. The dragonfly nymph has a fast, broad jaw with sharp, curved pinchers and, just like the adult he will become, can catch anything he chooses to go after.

All of these maneuvers work best for insects if the temperatures remain stable. Snow or frozen leaf litter help keep temps underground constant.

Insects are ubiquitous, mysterious and magical. They can change shape during several stages (instars) of their development from egg to adult. They are vital to our ecosystem as pollinators and are a necessary link in the food chain.

In retrospect we, the caretakers of our forests, can appreciate all of the forest life being generated during the winter quiet. When we hear the buzz of insects in spring we know our forests are ready for new growth and new life.

(Betsy Trammell, Louisiana tree farm forest landowner and CenLa Master Naturalist.)


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