Why Does Spider Activity Increase at Certain Times of Year?

Spring: Hatching, Mostly Unnoticed

Egg sacs laid the previous year hatch as temperatures rise, producing very large numbers of tiny spiderlings. Most disperse outdoors and most do not survive.

People rarely notice this at all, which is why spring feels like a quiet time for spiders even though it is the point of maximum numbers.

Summer: Growing, and Following the Insects

Spiders grow through the summer as the insect population peaks, and the visible activity is mostly outdoors — webs on fences, sheds, outbuildings and around outside lights.

Indoors it is generally quiet. Anything you do notice tends to be around windows and doorways, where the light is pulling prey in.

Early Autumn: The One Everybody Notices

For two or three weeks, typically September, large house spiders appear indoors, often running across a floor in the evening. These are adult males that have matured and are wandering to find a female.

They are not living in your house, they are not a sign of an infestation, they were not attracted by anything you did, and they stop on their own. If that is your situation, no treatment is worth buying and we will tell you so rather than take the booking.

Late Autumn and Winter: Settling

Egg sacs are produced and tucked into sheltered corners, reveals and outbuilding roof lines. Activity falls away, and surviving spiders overwinter in garages, sheds, lofts and cellars.

This is the best time of year to clear webs and egg sacs, because removing an egg sac in November removes several hundred spiderlings from the following spring. It is the highest-value ten minutes in the spider calendar and almost nobody does it.

Which Seasonal Surges Are Worth Acting On

Not September. Do act on a population that is present all year in the same place, a garage or cellar that is heavily colonised, webs that rebuild within days of being cleared, or spiders concentrated in one room, which usually points at an insect supply worth investigating.

Where there is a genuine persistent problem, treatment is £180 for the first room and £60 for each additional one, and it works best in early autumn or spring. But the honest answer for most September calls is that it will pass.