Silverfish And Earwigs: Two Damp Problems That Are Not The Same

Silverfish and earwigs both turn up on damp Ohio floors, and they mean opposite things. A silverfish lives in the house. It breeds indoors, in humid air, and it has usually been there longer than you think. An earwig came in from the mulch bed through a gap at ground level. One is an air problem. The other is a doorway.

Late September in Stark County is a good week to sort out which one you have. A warm wet stretch keeps block walls and crawl spaces holding moisture, and the first cool nights start moving outdoor insects toward warm foundations. The two pests get noticed in the same two weeks, for completely different reasons.

How Do You Tell A Silverfish From An Earwig?

Look at the back end. An earwig carries a pair of forceps, called cerci, at the tip of the abdomen, and Ohio State University Extension describes the European earwig as half an inch to three quarters of an inch long, with banded legs and a reddish head. A silverfish has nothing back there but three long bristles. Its body is teardrop shaped and covered in silvery scales, and it moves in a fast wriggle along a baseboard before disappearing into a crack.

Why Silverfish Are Already Living In The House

Humidity is nearly the whole answer. The University of California Statewide IPM Program puts the silverfish requirement at 75 to 95 percent relative humidity, with a preference for temperatures around 70 to 80 degrees Fahrenheit. Ohio State University Extension places them in damp, cool rooms: basements and laundry rooms, and in bathtubs, sinks and washbasins, where they fall in and cannot climb the smooth sides back out. That is why so many people meet their first one at 6 am in an empty tub.

Their close relative wants the opposite conditions. Ohio State University Extension puts firebrats in hot, humid places such as attics in summer and furnaces, fireplaces and heat pipes in winter, and UC IPM says they do best above 90 degrees Fahrenheit, with an optimum of 98 to 102 degrees, in humidity as low as 30 percent. The same Ohio house can hold both, three floors apart.

The timeline explains why nobody notices the start of it. Ohio State University Extension says silverfish and firebrats may reach maturity in 3 to 24 months and that adults may live two to eight years. An insect with that lifespan does not arrive in a wave. It accumulates, quietly, behind whatever you stacked against the basement wall.

Food almost never runs short. The same Ohio State fact sheet lists glue, wallpaper paste, book bindings, paper, photographs, starch in clothing, cotton, linen and rayon fabrics, wheat flour, cereals, dried meats, leather and dead insects. Read that list again and picture a cardboard box of old tax returns and a bin of winter clothes sitting on a concrete floor.

Cleaning does less than people hope, and Ohio State says so outright: sanitation is important but not entirely effective at reducing populations, because the insects live between wall partitions, in insulation materials, in books and papers and among bookshelves. Nobody vacuums a wall void.

Why Earwigs Turn Up All At Once

Because they were already outside in numbers, and something moved them. Penn State Extension describes earwigs gathering in large numbers under boards, in tree holes, under decaying bark and anywhere else moist and dark, and notes that when weather turns very hot and dry they seek the cool refuge of a basement or a garage. Of the species in this region, Penn State identifies the European earwig as the one likely to come looking for shelter in a house.

The numbers come from a nest with a mother in it. University of Florida IFAS Extension reports a first batch of 30 to 55 eggs, gathered into a pile in a shallow hole that the female stands guard over, handling the eggs repeatedly to keep fungus from growing on them. That is uncommon care for an insect. The same publication describes one generation a year, with some females producing a smaller second brood, and notes that first-brood eggs take about 70 days to hatch in cool spring temperatures while eggs laid in late spring or summer hatch in roughly 20.

They also travel on foot. Ohio State University Extension notes that European earwigs have wings while ringlegged earwigs are wingless, and that earwigs rarely fly, folding their wings into an origami-like arrangement of up to 20 folds. So an earwig on your laundry room floor did not come through a second-story window. It walked in at ground level, under a door sweep or through the gap around a hose bib.

The good news is the part everyone worries about. Ohio State University Extension states that earwigs are harmless to people and do not seek to hide inside ears, and Penn State Extension says the pinch from the cerci is harmless. The damage they do is outdoors, where Ohio State notes they can hurt seedlings badly and chew large holes in flowers and specialty crops.

What The Dampness Is Actually Telling You

Both insects are reporting on conditions, so conditions are what you change. Work this list from the yard inward, because treating a floor while the mulch bed keeps producing earwigs is a chore you get to repeat.

• Pull mulch, leaf piles and grass clippings back off the foundation. Penn State Extension makes eliminating those breeding and nesting places the first step for earwigs, and names decaying vegetable matter around the home specifically.
• Keep gutters, roof drains and downspouts clear and flowing. The EPA lists this next to fixing leaking pipes and faucets as basic moisture management for a building.
• Fix the leak before you treat anything. A dripping trap under a basement sink can support a silverfish population by itself.
• Bring the relative humidity down. EPA mold guidance says to keep indoor humidity below 60 percent, and ideally between 30 and 50 percent. Set that against the 75 to 95 percent UC IPM says silverfish require and you can see why a dehumidifier earns its keep in an Ohio basement.
• Close the ground-level gaps. The EPA lists caulk, knitted copper mesh, steel wool and foam insulation for blocking openings around pipes, along with weatherstripping on doors and windows.
• Get paper and fabric off the concrete and into sealed bins. Cardboard is harborage and food in the same object.

When Is It Worth Calling Somebody?

When you have fixed the conditions and they keep appearing, or when the harborage is somewhere you cannot reach. Silverfish living in blown insulation or between wall partitions are past the help of anything you can do from the living side of the drywall. An earwig population breeding in a bed of mulch against the house will keep resupplying the basement for as long as that bed is there.

That is the case for treating on a schedule instead of on sighting. Our State Shield Essential plan is quarterly, four visits a year, timed to break egg cycles rather than to chase whatever crossed the floor last Tuesday. It covers ants, spiders, millipedes, centipedes, cockroaches, mice, rats, bees, wasps and seasonal invaders, and if pests come back between treatments, so do we, at no cost.

If you are still not sure what you swept up, our occasional invaders library covers earwigs and the rest of the damp basement crowd. We work across North Canton and Stark, Summit, Portage, Wayne and Tuscarawas counties. Ask for a free estimate through our request form or call 330-494-6199.