A Month-by-Month Pest Calendar

January to March

Rodents Indoors, and the First Queens

The rodent season is still running and this is when it peaks indoors. A few mice that came in during the autumn are a population by now, because mice breed through the winter in a heated house on a three to four week cycle.

Cluster flies wake on the first mild day and appear at south-facing windows in numbers, which alarms people and is harmless.

From late February, queen wasps and queen ants that overwintered start moving. A queen wasp bumbling about a loft in March is looking for somewhere to start, and this is the cheapest moment of the whole year to deal with a nest that does not exist yet.

The job for these months: if you have heard anything in the loft over winter, deal with it now, before the spring litters.

Photographs on this page are for illustration purposes only.

April to June

Everything Starts

Wasp nests are founded in April and May by a single queen. Through to June a nest is small, quiet and easy — a golf ball, then a tennis ball. Almost nobody rings, because almost nobody notices.

Ants become active above ground from May. The colony was there all winter under the paving; warmth simply starts it foraging, and the first trail on a kitchen worktop is usually the first anyone knows of it.

Fleas pick up as temperatures rise, and squirrel calls cluster here because the spring litter is in the loft and suddenly audible.

The job for these months: walk round the outside of the house and look up. A nest found in May is trivial. The same nest in August is a job.

July to September

The Loudest Quarter

This is the busiest stretch of the year and it is almost entirely insects.

Wasps peak hard. A nest that was a curiosity in June is thousands of workers by August, and as the season ends and the colony stops rearing brood the workers switch to sugar — which is when they start appearing at pub tables, bins and windfall fruit and everyone rings at once.

Flying ant day falls somewhere in July or August, triggered by a warm, humid, still afternoon, and rolls across the country with the weather rather than happening on a fixed date.

Ant trails indoors are at their worst, and paving damage becomes visible as excavated sand builds up between blocks.

The job for these months: deal with wasps promptly, especially near a door, a path or where children play. And if ants are lifting your paving, treat the colony now rather than re-sanding in October and repeating this next year.

October to December

The Handover

The insects stop and the rodents start, and the changeover is sharp. Wasp colonies die off — only new queens survive, tucked away individually — and by November a nest is an empty shell that will not be reused.

Mice and rats move towards buildings as the ground gets cold and wet and outdoor food runs out. This is when the autumn proofing you did or did not do declares itself.

Carpet moths carry on regardless, because central heating suits them, and they do it in the places you stop vacuuming as the house fills up for Christmas.

Bed bugs travel home with people over the holidays.

The job for these months: the proofing, in October, before anything is in. Airbricks, door thresholds, service entries, bird feeding moved away from the walls.

The pattern

Two Seasons, Not Twelve

Underneath the detail it is simpler than a calendar suggests. Roughly April to September is insects and is driven by temperature. Roughly October to March is rodents and is driven by shelter.

Which gives two moments that are worth more than all the rest: a look round the outside of the house in May, when nests are small enough to be nothing, and a proofing pass in October, before the rodents arrive. Everything else on this page is reacting.

Short answers

Questions, Briefly

Where to go next

The Pages That Answer This