Earwigs in Winnipeg: maternal care, the ear myth, and why the treatment belongs outside

What we're dealing with

The European earwig, Forficula auricularia, is an omnivorous insect native to Europe, western Asia and North Africa, now invasive across North America, Australia and New Zealand.¹ It is the earwig in Winnipeg yards, and essentially the only one people encounter here.

Adults are 12–15 mm, reddish-brown, elongate and flattened, with the unmistakable forceps-like cerci at the rear. The forceps are sexually dimorphic and are the reliable field character: curved in males, straight in females.¹ Concealed hindwings unfold to a shape resembling a human ear — which inspired both the common name and the specific epithet auricularia.¹

The taxonomy has recently been complicated. F. auricularia is now understood as a species complex, with Forficula dentata and Forficula mediterranea morphologically indistinguishable but reproductively isolated, separated by mitochondrial DNA and geographic distribution.¹ Temperate populations typically produce one brood annually while warmer regions may support two.¹ Manitoba is firmly a one-brood climate.

Life stages and cycle length

Earwigs are hemimetabolous — egg, nymph, adult — with four or five nymphal instars and no pupal stage. What sets them apart from every other insect in this library is what happens between the egg and the nymph.

One generation per year in this climate, with maternal care occupying the whole winter and early spring. That single-brood cycle means the population you see in August is the entire year's output — and it also means a cold, wet spring genuinely reduces the late-summer numbers.

Harborage and feeding

Earwigs are nocturnal and require damp, tight shelter through the day. Harborage is consistently:

• Mulch beds, particularly deep mulch in direct contact with a foundation
• Leaf litter, grass clippings and plant debris along walls
• Under stones, paving slabs, planters and landscape timbers
• Beneath deck boards and in the gap behind siding
• In compost, woodpiles and stacked material
• Indoors: bathrooms, basement floors, under sinks — but only as wanderers, not residents

They are genuinely omnivorous,¹ feeding on decaying plant material, algae, soft foliage and flower petals, and also on live prey including aphids, mites and insect eggs. In North America they are known as a household pest, invading crevices and consuming pantry foods.¹

The important framing for a homeowner: earwigs do not breed indoors in Manitoba. The nest is an underground chamber outdoors.¹ Individuals wander in when outdoor conditions dry out or when populations peak, and they die there. There is no indoor population to eliminate, which is why interior spraying is close to pointless and exterior work does everything.

Maternal care and family life

This is the part that makes earwigs genuinely remarkable, and it is why they appear in far more research papers than their pest status would suggest.

The species exhibits extended maternal care, with females guarding eggs and nymphs in underground nests.¹ The mother does not simply sit with the clutch. She gathers scattered eggs back together, guards them against predators, and grooms them individually — removing fungal spores that would otherwise destroy the brood. Three distinct behaviours: egg gathering, egg guarding and egg grooming.⁵

This is facultative care — mothers provide pre- and post-hatching care that enhances offspring survival yet may incur costs to future reproduction.⁶ Experimental work manipulating the presence of tending mothers and brood size found that larvae growing in broods tended by their mother, or in reduced-size broods, showed higher survival probability than larvae in untended or large broods — exactly as predicted if maternal care is beneficial and shaped by a trade-off between offspring number and quality.⁴

Earwigs are not eusocial. There is no queen, no caste, no colony. What exists is a mother and her brood in a chamber for a season — subsocial rather than social, and that intermediate position is precisely what makes them useful.

Behaviour and defence

Earwigs are strictly nocturnal and strongly thigmotactic, wedging into gaps that contact them on multiple surfaces. Daytime sightings mean a disturbed harbourage — a lifted stone, a moved planter.

They aggregate, often in mixed stages, and adults and larvae share habitats.⁷ That aggregation is why lifting a paving slab in August can reveal dozens at once.

Defence works on two levels. The forceps are deployed in mechanical defence and are present even in larvae.⁷ A large male can deliver a pinch that is startling but breaks no skin and carries no venom.

The second level is chemical. Earwigs possess paired projections on the third and fourth abdominal tergites marking the openings of defensive glands that mediate chemical defence, and these are present in larvae as well as adults.⁷ Related species take this further — the giant earwig Labidura riparia mimics rotting-flesh odour to deceive vertebrate predators.³

They fly rarely despite having functional hindwings. Most dispersal is by walking, which is why exclusion at ground level is effective.

Where in Winnipeg

Earwig pressure in this city is almost entirely a landscaping question, and it is highly responsive to what is done in the metre closest to the foundation.

• Properties with deep mulch against the foundation. The single strongest predictor. Mulch in direct ground contact with a wall is ideal harbourage and puts it directly at the entry points.
• Heavily irrigated or shaded yards, where soil stays damp through the summer — north-facing beds, dense hedging, and areas under mature canopy.
• River and creek corridors along the Assiniboine, Red and Seine, where leaf litter and moist banks support high outdoor densities.
• Properties with poor drainage — downspouts discharging at the foundation, negative grade, or areas that pond after a storm. Winnipeg's clay soils hold water, which extends the damp period they depend on.
• Yards with extensive hardscaping, stones, slabs and edging, each providing a daytime shelter.

The seasonal peak is mid to late summer, with complaints rising through July and August and falling away with the first cool nights. A dry August pushes them indoors looking for moisture; a wet one keeps them outside.

Natural control factors

Earwigs have an unusually well-documented set of natural enemies, which is a by-product of decades of research attention on the species.

• Parasitoid flies. The tachinid flies Triarthria setipennis and Ocytata pallipes, and the parasitoid fly Bigonicheta spinipennis, all attack earwigs and have been used as biological control agents.¹
• Entomopathogenic fungi. Erynia forficulae and Metarhizium anisopliae both infect earwigs.¹
• Nematodes. Mermis nigrescens parasitises them.¹
• Birds, which take them readily where they are exposed.¹
• Weather. Cold wet springs during the underground brood period reduce the year's output; dry summers force wandering but also cause mortality.

Worth weighing: earwigs are predators of aphids, mites and insect eggs, and are treated as beneficial in some orchard systems. In a Winnipeg garden they are doing real work on soft-bodied pests. The honest recommendation is often to reduce harbourage against the house and leave the rest of the yard alone.

DIY: what works, what backfires

Our treatment process

1. Exterior harbourage survey. Mulch depth and contact, leaf litter, stones, planters, deck undersides, drainage faults. This is the diagnosis, and it is done outdoors.
2. Perimeter residual band at the foundation, thresholds and entry points — the interception line between harbourage and house.
3. Treatment of exterior harbourage in mulch beds, along retaining walls and under decking where populations concentrate.
4. Crack-and-crevice application at interior entry routes — thresholds, weep holes, utility penetrations — rather than broadcast interior work.
5. Written harbourage reduction advice: mulch depth and setback, ground contact, drainage, debris clearance. This is the part that holds.
6. Return visit on request, though in most cases a single well-timed perimeter treatment plus landscaping changes resolves it for the season.

We will tell you honestly that this is one of the cheaper problems on our list to fix, and that a good share of the fix costs nothing but an afternoon with a rake.

The chemistry, and how it kills

One caution from the literature worth flagging: earwigs are subject to insecticide resistance and tolerance development in conventional orchards.¹ Repeated pyrethroid use against the same population is not risk-free, and it is another argument for leading with harbourage reduction and physical traps rather than annual spraying.

Treatment timeline

Why entomologists study earwigs

A model for the origins of family life

The European earwig has become an important model for studies of maternal care, sexual selection, sociality and host–parasite interactions,² and behavioural ecologists have used it extensively to investigate the early evolution of group-living and family life.² The reason is its intermediate position: care exists, but it is optional, costly and measurable — so the trade-offs that shaped the evolution of parenthood can be manipulated experimentally in a way that is impossible in a bee or an ant.

The Annual Review of Entomology devoted a full review to the biology and social life of earwigs,³ which is not a status many household nuisance insects achieve.

The genome, 2022

Detailed genetic investigation of the species had long been hindered by a lack of genomic resources. A team at the University of Otago produced a hybrid genome assembly and annotation for F. auricularia subspecies B in 2022,² opening the species to the molecular work its behavioural literature had outrun.

Hormones, heat and maternal care

Recent work has tested whether juvenile hormone regulates parental care, as had been proposed for insects generally. Researchers manipulated JH levels in nearly 500 post-oviposition females using JH III, the agonists methoprene and pyriproxyfen, and the production inhibitor precocene I, then quantified egg gathering, egg guarding and egg grooming. Consistent with a positive role for JH in promoting maternal care, inhibiting JH synthesis reduced all three behaviours.⁵

The same body of work examined heat waves during egg development, finding that thermal stress affected two of the three care behaviours and the level of maternal investment measured by mother weight variation — including how likely mothers were to collect scattered eggs and how often they contacted them.⁵

Chemical defence in the young

Research on chemical defence in earwig larvae notes that few studies have considered the natural enemies of earwig larvae, and that little is known about the active defence strategies of the soft-bodied stages between maternal custody and adulthood.⁷ Since larvae and adults share habitats and frequently aggregate in mixed stages, they likely face similar predator pressure and may have evolved similar defences — and larvae do already possess both the forceps and the defensive gland openings.⁷

Cryptic species and climate

The species complex question is active, with work on alternative reproductive strategies in two cryptic species of the European earwig complex,⁸ and on climate and human influence shaping the distribution limits of this invasive species.⁸ There is no Manitoba-specific work on which member of the complex is present here, which is a genuine open question for a pest this common in prairie yards.

Cultural history

The ear myth, traced. The belief that earwigs enter the ear and bore into the brain is attested across medieval Europe and appears in Old English as ēarwicga — literally ear-beetle. The equivalent exists in German (Ohrwurm), French (perce-oreille, ear-piercer) and elsewhere, which suggests the folklore predates those languages diverging. The actual origin is the ear-like shape of the unfolded hindwing.¹

Ohrwurm. The German word for earwig also means an earworm — a tune stuck in your head. English borrowed the concept and calqued the word. Every time someone complains about a song they cannot shake, they are invoking this insect.

The forceps question. Male forceps dimorphism has been studied in the context of sperm competition,³ making the earwig's most conspicuous feature a subject of genuine sexual selection research rather than merely a defensive tool.

Handedness in insects. One of the odder findings in the earwig literature: male earwigs show an unusual bias in the use of their lateral left and right sexual organs despite no conspicuous anatomical difference between them, and around 90% of giant earwig (Labidura riparia) males prefer the right — a bias compared directly to human right-handedness and studied for what it reveals about the evolutionary origins of lateralisation.²

The Winnipeg bathtub. The overwhelmingly common local encounter is an earwig stranded in a bathtub or sink overnight in August. They fell in and could not climb out. It is not where they live, and it is not an infestation — it is a wanderer that made a mistake.

The internet era. Earwigs are a permanent fixture of "is this dangerous" posts, and the answer is always no. The more interesting recent development is that their standing as a serious research model for family life has started leaking into popular science writing — which means the insect people fear will crawl into their ear is also one of the animals teaching us how parenting evolved.

References

1. Forficula auricularia (European earwig): identification, taxonomy and species complex, forceps dimorphism, maternal care, brood number by climate, natural enemies, physical traps, insecticide resistance in orchards. species guide
2. Bhattarai, U.R., Katuwal, M., Poulin, R., Gemmell, N.J. & Dowle, E. (2022). Genome assembly and annotation of the European earwig Forficula auricularia (subspecies B). G3. doi.org/10.1093/g3journal/jkac199
3. The biology and social life of earwigs (Dermaptera). Annual Review of Entomology. annualreviews.org
4. Benefits and costs of earwig (Forficula auricularia) family life. Behavioral Ecology and Sociobiology. doi.org/10.1007/s00265-007-0381-7
5. Heat waves during egg development alter maternal care and offspring quality in the European earwig; and juvenile hormone manipulation of egg gathering, guarding and grooming. Journal of Insect Physiology. sciencedirect.com
6. Parental care and family dynamics in European earwigs — facultative maternal care and reproductive trade-offs. Nature Research Intelligence. nature.com
7. The chemical defense in larvae of the earwig Forficula auricularia. Journal of Insect Physiology. sciencedirect.com
8. Alternative reproductive strategies in two cryptic species of the European earwig complex. The Science of Nature. Includes Hill et al. (2019) on climate, human influence and distribution limits. doi.org/10.1007/s00114-025-01999-9