The short answer
Bed bug interceptors are small double-walled cups that go under each bed leg. Bed bugs can climb into them from the floor but struggle to climb the smooth inner wall out, so they are trapped where you can see them. They are a good way to confirm bed bugs and to check a treatment has worked, but they do not clear an infestation on their own.
If you are getting bitten but cannot find anything on the mattress, or a treatment has finished and you want to know it worked, interceptors are one of the cheapest and most useful things you can buy. They are not a cure. They are a way of finding out.
What an interceptor is
A bed bug interceptor is a plastic cup, usually 10 to 15cm across, with two walls: an outer ring and an inner well. The bed leg stands in the inner well. The outside of the cup is rough or textured so a bed bug can climb up it easily. The inside walls are smooth and slippery.
A bed bug walking across the floor towards the bed climbs the rough outside, drops into the gap between the walls, and then cannot climb the smooth surface to get out. A bug coming down from the bed can fall into the inner well the same way. Either way, it ends up in the cup where you can see it.
They work because bed bugs cannot jump or fly. The only way onto a bed that stands clear of the wall is up the legs. Our guide on whether bed bugs jump or fly explains why.
How to set them up
- Pull the bed away from the wall by a few centimetres. If the headboard or the duvet touches the wall, bed bugs can walk straight round the cups.
- Tuck the bedding in. Nothing should hang down to the floor, including the valance.
- Put one cup under every leg. A divan with castors can usually sit in them too. If your bed sits flat on the floor with no legs, interceptors will not work; tell the pest controller instead.
- Keep them clean and dry. Dust or fluff in the cup gives bed bugs something to grip. Some people add a light dusting of talc to the inside to make it more slippery; check the maker’s instructions first.
- Do the same with the sofa if anyone sleeps or naps on it.
How often to check them
Look in every cup every few days with a torch, for at least a week or two. Bed bugs do not feed every night, so a cup that is empty after two nights does not prove much. Two weeks of empty cups, with no new bites, is a much better sign.
What a catch tells you
- Bed bugs in the outer ring have been walking in from the room: from the skirting, the furniture or the floor. The problem is not only in the bed.
- Bed bugs in the inner well came down from the bed. The mattress, base or frame is likely to be affected.
- Lots of small, pale bugs are young bed bugs, which means they are breeding.
- Other insects are worth noting too. Spiders, beetles and other crawling insects end up in cups as well, and if bed bugs never appear, that is useful information for a pest controller.
Keep anything you catch. Seal the cup in a clear bag, or tip the contents onto clear sticky tape. A professional can confirm what it is in seconds.
What interceptors cannot do
Be clear about their limits:
- They do not clear an infestation. Bed bugs hide in the mattress, the base and the room, and many never walk into a cup.
- They do not stop bites if bugs are already living in the bed itself.
- They do not work if the bed touches anything else, such as the wall, a bedside table or bedding on the floor.
- An empty cup is not a guarantee. It is evidence, not proof.
Cups are a monitoring tool. For actually clearing bed bugs, NHS guidance is to bring in the council or a pest control company.
When they are most useful
Before you pay for treatment
If you have bites but have not seen a bug, a week or two of interceptors can settle whether it is bed bugs or something else, before you book. Fleas and mites will not turn up in the cups in the same way. If you need an answer faster, book a professional inspection.
After a treatment
Interceptors are a simple way to keep an eye on things between spray visits and for a few weeks after the last one. Many pest controllers use them for exactly this. If bed bugs turn up in the cups after treatment has finished, tell the firm straight away; most include a follow-up for this reason.
In rented and shared houses
In a student house or HMO, cups under the beds in the rooms next to an affected one are a cheap early warning. Landlords sometimes leave them in place between tenancies.
Where to get them
Interceptor cups are sold online and in some hardware shops, usually in packs of four. They are inexpensive and reusable.
If the cups have caught something, or you simply want it sorted, fill in the short form below and we will find a local Sheffield pest controller to come and look.