How do I get rid of mice and roaches for good?

The library’s two pest pages agree on one thing before anything else: the animal you can see is not the problem. The hole is, or the colony is. The mice page names the two products people buy first as the two to avoid; the roach page’s equivalent is do not spray, bait instead.

Mice: seal the gaps. Seal the gaps the mice come through says you can catch mice all winter and still have mice, because catching them is not the thing that ends it. Every mouse came through a gap, where a pipe enters a wall, under a door, around a vent; if you can get a pencil into it, something can get through it. What holds is steel wool stuffed into the gap with caulk over it, or hardware cloth across anything larger; expanding foam on its own is not one of them, because they chew through it. The traps, briefly: peanut butter on a snap trap, smeared rather than dolloped, set along walls because mice travel edges. A well-set snap trap kills in an instant; a badly set one can injure, so place carefully rather than placing many. The page’s safety line is the part to read before the shop: poison kills slowly and internally, so the animal dies inside a wall and you get a smell you cannot reach for weeks, and it stays poisonous after death for the cats, dogs, owls and hawks that eat it; glue boards were condemned there repeatedly by people who had used one, because they hold an animal until it starves. The humane-looking option split its people hard: a mouse released nearby comes straight back, and one released far away has no shelter and no food store. Nobody settled it.

Roaches: bait where they hide, and never spray. Bait it where it hides starts with the midnight kitchen light and the shame, and says the ones who cleared it explain why a spotless kitchen is not the point. First the triage, for North American homes: one big roach wandered in from outside and possibly means a leak; small tan ones with two stripes mean a colony living indoors. Then put slow poison where they hide, a barely visible film of boric acid in the cracks and under appliances, or gel bait in the hinges and gaps, and they carry it back to the rest, because roaches eat their dead. A spray kills the one you see and works against the bait. The safety line follows the regulators, not the account that called boric acid as harmless as salt: infants who have eaten it have been seriously harmed, it irritates the lungs if breathed, so it goes only where small hands and paws cannot reach, and enclosed bait stations are the version for a household with toddlers or pets that lick their paws. The page carries the do-it-yourself-or-pay-a-professional argument with both sides; its decider is the household and the building, and a shared building with an untreated source next door favours the professional.

Bees in the wall are a different call. For honeybees, call a beekeeper first redirects the first instinct: if the insects are honeybees, call a local beekeeper before any exterminator. A swarm clustered on a branch is often collected free, because a hobbyist gains a colony; an established colony inside a wall is paid work, structural opening and full comb removal, and the page carries that argument about who pays with both sides. Killing a wall colony leaves pounds of honey and brood decomposing inside the wall, attracting ants, roaches and rodents. Photograph first, identify second.

Who this is not for. If you rent, the mice page says the gaps are the building’s and the building is not yours: in many places sealing entry points is the landlord’s repair obligation, worth checking where you live because it varies, so report it in writing, describe where the gaps are, and keep what comes back. The roach page adds that in a shared building the source may be next door, and a tenant should check whether the landlord is obliged before paying anyone. And if a colony of bees behaves aggressively, pursuing at a distance, stop diagnosing and call professionals; the beekeepers on that page will not touch those either.