Kids notice it before the adults do. One week the sidewalk has roly-polies on it and grasshoppers are jumping out of the dry grass, and then after the first hard freeze along the Front Range, the yard goes quiet. The natural question, where did they all go, has a better answer than “they died.” Most of Colorado’s insects and their small neighbors are not gone. They are hiding, sleeping or waiting out the cold as eggs, and a lot of that is happening a few inches from your back door. This guide pulls the answer from Colorado State University Extension and gives you a short investigation to run with your kids before the snow settles in.
Four ways Colorado insects get through winter
CSU Extension’s PlantTalk Colorado fact sheet on insect overwintering lays out the strategies. The first is the one kids guess: some insects simply leave. Monarch butterflies travel south for the winter and come back north in spring. A second group does something close to hibernating. Lady beetles and box elder bugs overwinter as adults, which the fact sheet compares to a bear hibernating in a cave; those are the ladybugs that turn up in a sunny window in January.
The third strategy has a name worth teaching: diapause. CSU describes it as a state in which insects stop growing and developing. The insect does not wake up until it has been through a required stretch of cold, or until longer days signal that spring has arrived. The fourth is pure chemistry. Some insects add glycerol to their cells, and the fact sheet calls it what it is, antifreeze. Whatever the strategy, CSU says most insects spend the winter below ground, under debris or in some other insulated spot. That is why a messy corner of the yard is a better science lab in October than a tidy one.
Who is sleeping where: eggs, pupae, larvae and adults
The same CSU sheet sorts common Colorado insects by the life stage they use to survive the cold, and it makes a good matching game for a kitchen-table lesson. Mosquitoes, grasshoppers, aphids and scale insects overwinter as eggs. Most butterflies spend the winter as pupae attached to objects above the ground, so a chrysalis on a fence rail is not dead, it is waiting. Two garden pests, the geranium budworm and the hornworm, pupate in packed earthen cells about three inches underground. Bark beetles, including the mountain pine beetle, and wood borers spend the winter as partly grown larvae under the bark of the trees they infested.
One more detail from the fact sheet surprises most grown-ups: the biggest threat to overwintering insects is not the coldest night of the year. It is the late-winter swing between very cold and very warm weather, the kind of February Colorado gets most years. The same swings threaten plants, which is why gardeners and bugs are rooting for the same steady winter.
What about roly-polies?
Roly-polies are the one critter most Colorado kids can find on demand, and they are not insects at all. CSU Extension’s fact sheet on millipedes, centipedes and sowbugs describes pillbugs, the ones that roll up, and their flatter cousins the sowbugs as small, gray crustaceans usually found outdoors under rocks or other cover. They eat decaying plant material and occasionally small plants, and the sheet is clear that they do not bite and are harmless to humans. The University of California’s pest management program adds the numbers kids like: pillbugs have seven pairs of legs, eggs hatch about a month after they are produced, young ones molt every week or two while they mature, and adults can live two to five years.
Those long lives are the clue to their winter. Neither university sheet spells out how deep a pillbug goes when the ground freezes, and we will not guess for them, but both say the same thing about where pillbugs live at any time of year: hidden under organic litter, rocks and other debris, in places that stay damp, because a pillbug dries out easily. In practice that means the leaf pile you have not raked yet is the best place to look for them this month, and the base of a stone or a flowerpot sitting on soil is second best. CSU notes that pillbugs sometimes wander into houses, mostly after long wet spells in spring, and that they do not last long indoors.
If your kids already know roly-polies from Curio Power and the Roly-Polies, the Colorado children’s picture book by Linda Ellis, the book’s own roly-poly facts page lines up with the university sheets on the big points: crustaceans related to crabs and lobsters, breathing through gills, which is why they stay in damp spots, 14 legs, and a diet of decomposing leaves and vegetables. The book’s site also says a lost leg grows back in about a week, a detail we did not find in the university sources, so file that one under “ask the book.” Our earlier guide, Are roly-polies insects?, covers how to tell a pillbug from a sowbug. Disclosure: Curio Power and the Roly-Polies is a Holland Health Marketing client.
A 20-minute backyard investigation for October
These steps are Colorado Local’s suggestions, built on what the fact sheets say about where overwintering animals hide. Pick an afternoon above freezing, since the sheets say most of these animals are inactive in the cold, and bring a notebook, a magnifying glass if you have one and a small cup for a closer look.
- Check three habitats and keep a tally for each: under a leaf pile or mulch, under a rock or flowerpot that sits on bare soil, and along the sunny side of the house or fence. Predict first which spot will have the most life, then count.
- Sort what you find by strategy. A roly-poly or a beetle still moving is an adult riding out the cold under cover. A chrysalis stuck to a fence or a stem is a pupa. A cluster of tiny dots on a twig may be eggs. Nothing at all under the dry rock is a finding too: no moisture, no pillbugs.
- Test the “roll” gently. Touch a pillbug and a sowbug with a leaf. The pillbug curls into a ball; the sowbug runs. Put them back where you found them, because both need the damp.
- Leave one corner of the yard unraked until spring and label it the winter lab. Check it again after the first snow melts and compare the tally.
For a bigger outing, pair the backyard count with a visit to a nature center or a free outdoor event; this Saturday’s International Archaeology Day at Red Rocks is free and family friendly, and our homeschool nature listings run all fall.
Sources
- PlantTalk Colorado 1440: Insect Overwintering, Colorado State University Extension
- Fact Sheet 5.552: Millipedes, Centipedes, and Sowbugs, Colorado State University Extension
- Pillbugs and Sowbugs, University of California Statewide Integrated Pest Management Program
- Meet the Roly-Polies, Curio Power and the Roly-Polies
More like this: Family + Learning · Homeschool + Field Trips · Curio Power and the Roly-Polies · Are roly-polies insects? A backyard science guide for Colorado kids · Learn
