An interceptor trap is a cheap way to find out whether bed bugs are still active. It sits under a bed or sofa leg and catches bugs as they climb. However, it does not treat your home. Think of it as a smoke alarm, not a fire engine.
This guide explains how interceptors work, what research says about them, and how to use them well. It also covers the mistakes that make a trap miss bugs that are really there.
How an interceptor works
Most interceptors are two shallow dishes, one inside the other. You place one under each leg of the bed or sofa. A bed bug climbing up or down the leg drops into the gap between the dishes. The walls are smooth and often dusted with talc, so the bug cannot climb out.
This design uses two habits of bed bugs. First, they search for a sleeping host. Second, they climb rough surfaces easily. A rough outer wall helps them climb in, and a smooth inner wall traps them. Researchers call this a pitfall trap. Because it needs no bait, power or chemicals, it is simple to use.
What the research found
Traps often find bugs that a visual check misses. For example, in one Rutgers study of lightly infested apartments, interceptors left for seven days detected bed bugs in 70% of apartments with fewer than ten bugs. A careful visual inspection found them in 50%. In apartments with 11 to 35 bugs, the traps found them every time, against 60% for inspection (Wang et al., 2011).
An earlier field test points the same way. Researchers inspected thirteen apartments, removed the bugs they found, and then fitted interceptors. Inspections had found an average of 6.7 bugs per apartment. After seven days, the traps had caught an average of 8.8 per apartment. Of ten residents interviewed, only four had noticed bites (Wang, Gibb and Bennett, 2009).
So a quiet bed is not proof of a clear bed. Some people barely react to bites, and others mistake them for something else. The NHS bedbug page also warns that they can be hard to find.
How to use traps properly
Fit one under every leg of the bed and any upholstered chair or sofa where you sit. Then check that nothing gives the bugs a bridge across. Bed linen touching the floor, or a bed pushed against the wall, lets bugs bypass the trap. In the Rutgers apartments, such bridges may have cut the traps’ success.
Leave the traps in place for at least a week, and ideally longer. A Rutgers extension fact sheet says traps need at least a week to detect low numbers (Wang, Rutgers Cooperative Extension). Check them weekly with a torch, and tip any catch onto white paper. Keep a note of the date and the room.
Traps have limits, however. They do not suit furniture with very wide or missing legs. They also tell you little about an empty room, because nothing is there to draw the bugs out. Finally, they can only catch bugs that cross between the furniture and the floor.
Using traps after a treatment
After a professional heat treatment or a steam session, traps give you evidence instead of guesswork. A catch tells you the problem is not over. An empty trap, week after week, is encouraging. Even so, it is not a guarantee. Our post on how long heat treatment takes explains how long a single visit takes.
In a later Rutgers trial, researchers inspected traps every two weeks. They counted an apartment as clear only after eight straight weeks of empty traps and a clean visual inspection (Cooper, Wang and Singh, 2015). That is a research standard, not a legal one. Therefore, one clean week proves very little.
The same trial tested trapping as a treatment. Interceptors left in place cut bug counts, and half the apartments were clear at 16 weeks. That is useful, but it also means half were not. The Rutgers fact sheet therefore advises against relying on monitors alone for control.
Our guide on what to do after treatment explains how to record evidence and when to call your provider back. If traps keep catching bugs after a visit, then ask whether the product or method suits your case. The page on treatment resistance covers why some sprays fail.
Where traps fit in the bigger plan
An interceptor sits well alongside other steps, but it replaces none of them. Before a visit, for example, our post on preparing a room for treatment shows how to clear bridges and clutter first. You can compare options on the treatment comparison page.
Traps also help you judge DIY efforts, because they show whether anything changed. If you are tempted by sprays, read do shop-bought sprays work first. Our DIY guide lists which steps are safe and which are not.
Once the bugs are gone, travel and laundry habits keep them away. Our posts on washing and drying clothes and avoiding bugs after travel cover those. When you want to judge success, read signs a treatment has worked. If you want a chemical-free option for cracks, see diatomaceous earth and other dusts, and check the desiccant dust guide too.
Read the product label rules before you use any dust or spray near a trap. The label, not the trap, decides where a product may go.
Sources
- Wang C, Tsai W-T, Cooper R, White J (2011). Effectiveness of bed bug monitors for detecting and trapping bed bugs in apartments. Journal of Economic Entomology 104(1):274–278.
- Wang C, Gibb TJ, Bennett GW (2009). Interceptors assist in bed bug monitoring. Pest Control Technology, April 2009.
- Cooper R, Wang C, Singh N (2015). Effects of various interventions, including mass trapping with passive pitfall traps, on low-level bed bug populations in apartments. Journal of Economic Entomology.
- Wang C. FS1117: Detecting bed bugs using bed bug monitors. Rutgers Cooperative Extension.
- NHS. Bedbugs: how to get rid of them.