Autumn: the pests that move indoors, and what to do this week

The first cold nights change who you share the house with. A spider turns up in the bath, something scratches in the loft at dusk, and a sunny window fills with slow, dozy flies. Most of this is the season, not a sign that anything has gone wrong. A few of these visitors are worth acting on this week. The rest mostly need a vacuum and a little patience.

One note first. This is autumn in places with cool or cold winters. If you are reading in the southern hemisphere, it is spring where you are, so save this for March. And in warm climates the shift is smaller: cockroaches and mosquitoes carry on much as before, and wasp colonies can last through the winter.

Spiders: more visible, not always more

Autumn is when people notice spiders most. In many places that is because adult male house spiders start wandering to find a mate, not because a crowd has just moved in from the garden. Plenty of them were living quietly behind the furniture all summer.

No home is ever spider-free, but you can make yours a poor place to settle. Close gaps around windows and pipes, fit fine mesh over vents without blocking them, switch off outdoor lights you do not need, and vacuum webs and egg sacs every week or two. Fewer insects means fewer spiders. The full plan is in how to keep spiders out. If there is one in the room right now and you cannot face it, catching a big spider when you are scared of them is the gentle way. And if you do not recognise it, do not handle it: is this spider dangerous? covers what to do next.

Mice: the one to act on now

As nights cool, mice look for warmth and shelter, and a house with a small gap behind the boiler is an obvious choice. Autumn is the time to close those gaps, before anything has settled in for the winter.

Look low and slowly with a torch: where pipes and cables come through walls, behind the cooker, under outside doors, around the loft hatch. Pack gaps with steel wool and seal over it, because foam on its own gets chewed. Never block an air brick or vent. Cover it with metal mesh instead. Our guide to sealing gaps goes through each spot.

Already hearing them, or finding droppings? Put food away, catch the ones inside with live catch traps checked every morning, and seal the last gaps once the catches stop. Why mice keep coming back explains why proofing beats any product, and the mice and rats guide has the full plan. We do not recommend poison or glue boards. Glue and bucket traps explains why, and poison carries its own risks for cats and dogs (rat poison with pets).

Scratching overhead that sounds bigger than a mouse may be squirrels or another animal in the roof. Animals in the roof covers getting them out humanely. Many wild animals are protected by law, so check before you seal anything shut.

Wasps at the end of their season

Late-season wasps have a reputation for being dozy and short-tempered. What has really changed is their job. The nest needs them less, and they go looking for sugar, which is why they find your drink, the fruit bowl and the bin.

Where winters are cold, a common wasp nest lasts one season. The workers die off as it gets colder, new queens leave to spend the winter somewhere sheltered, and the old nest is not used again. A nest that is out of the way can often be left. Does a wasp nest need removing? walks through when to wait and when to call a professional, and wasps keep getting into my bedroom covers the ones that find a way inside.

The classic autumn mistake is blocking the entrance while the nest is still active. Trapped wasps look for another way out, and that way can be into your rooms. Wait until it has been silent through some cold weather, then seal.

Stings: if someone who has been stung gets swelling of the face, lips or throat, has trouble breathing or feels faint, call emergency services straight away. For ordinary pain and swelling, a pharmacist can advise.

Cluster flies and ladybirds at the window

In some places, including the UK and parts of Europe and North America, autumn brings insects that come indoors to sit out the winter rather than to breed.

• Cluster flies are bigger and slower than house flies. They gather in lofts, roof spaces and upstairs window frames, and wake up sluggish on sunny days. They do not breed indoors. They came in through gaps around windows and eaves.
• Ladybirds, the harlequin (also called the Asian lady beetle) best known among them, can cluster in window frames, curtain folds and lofts. They do not breed indoors over winter. Squashed or handled roughly, they can leave a yellow fluid that stains, so try not to crush them.

For both, the vacuum is the right tool. Hoover them up and empty it outside. Fly spray is not much help: more come out of the gaps on the next sunny day. The lasting fix is sealing gaps around window frames and eaves, and fitting mesh over roof vents without blocking them, once the weather turns and they have left. If the loft is full of flies every year, a local pest controller can advise.

Silverfish, booklice and damp as the heating comes on

Windows stay shut, washing dries on radiators, the kitchen steams up. That extra moisture is exactly what silverfish and booklice live on. Neither says anything about how clean you are. Silverfish follow damp, not dirt, and booklice, much smaller and paler, follow it too (what are these tiny white bugs?).

The fix is the same for both. Run extractor fans, open a window for a while each day, wipe condensation off the glass in the morning, and dry washing outside or in a vented dryer when you can. Sort any drips under sinks. A dehumidifier helps in a room that stays damp. The silverfish guide has the rest. If you rent and the damp comes from the building, tell your landlord in writing with dated photos. How to document pests for your landlord covers what to send.

The weekend checklist

Most of this is free or close to it. Do it in this order.

1. Walk round the outside. Look for gaps where pipes and cables go in, damaged vent covers, gaps under doors and around window frames. Write them down.
2. Seal what you can reach. Steel wool and sealant for anything a mouse could use, sealant for cracks, a brush strip under outside doors, mesh over vents. Leave any gap that wasps are still using.
3. Take away the food. Pet bowls up at night, bird seed and dry food in hard sealed containers, a lid on every bin.
4. Clear the walls outside. Move log piles, leaf heaps and pots away from the house, and cut back plants that touch it.
5. Vacuum the quiet corners. Webs, egg sacs, window frames, under beds, the area around the loft hatch. Empty the vacuum outside.
6. Check the damp spots. Under sinks, behind the bath panel, the cupboard with the boiler or water tank. Fix drips and make sure the extractor fans work.
7. Put down monitor traps, dated. Kitchen, bathroom, by the back door. In a couple of weeks they tell you whether anything moved in. See how to use monitor traps.
8. Swap the wardrobe over carefully. Put summer clothes away clean and sealed, and look over the wool you take out for holes and larvae. Protecting wool and cashmere has the routine.

Kids and pets: sticky traps have no poison, but the glue sticks to fingers and fur, so slide them behind appliances, out of reach of children and pets. If you use any insect bait, follow the label on placement, and leave it out if there is nowhere out of reach.

What you can skip

Autumn is when the shelves fill with plug-in repellers. They do not keep mice or spiders out (do ultrasonic repellers work?). Conkers on the windowsill and peppermint spray are lovely traditions, not barriers. Spraying insecticide around the skirting does not close a single gap either. Your weekend is better spent on the list above.