Can Bed Bugs Bite While You Sit on a Sofa?

They Are Not Nocturnal. They Are Opportunistic

Bed bugs feed when a host is available and still. That usually means at night, because that is usually when people are available and still — but the driver is the host's behaviour rather than the clock.

Change the pattern and the feeding follows it. A night-shift worker who sleeps during the day gets bitten during the day. Somebody who spends three hours motionless on a sofa in the evening is offering exactly what a bed offers, at a different hour.

What Daytime Biting Tells You

Three things, and all of them matter for scoping the job.

1. There is a harbourage close to where you are sitting. They do not cross a house to feed. If somebody is bitten on a sofa, the population is in or very near that sofa
2. The living room is part of the job. Not a maybe — a room to be inspected and probably treated
3. It is not new. A sofa becoming a feeding site means either that somebody has been sleeping there, or that the infestation has been running long enough to extend beyond a bedroom

How Feeding Actually Works

Useful to know, because it explains several things people find puzzling.

• They are drawn by exhaled carbon dioxide and by warmth, then by certain chemicals on skin. It is why a host who moves rooms gets followed
• A meal takes a few minutes, after which the insect returns to its harbourage. They are not on a person for long
• They feed every few days rather than every night when they can. So bites appearing on some mornings and not others is normal and is not evidence of anything
• Reaction can be delayed by days, which means the night you were bitten and the morning you noticed may not be the same event

That last point causes a great deal of confusion, because people reasonably try to work out where they were the previous night. It is not a reliable exercise.

Bites Still Do Not Confirm It

Everything above assumes bed bugs have been established by physical evidence. Bites on their own do not settle it: reaction varies enormously between people, plenty of things bite, and skin reactions that are not bites at all can look similar.

A pharmacist or GP can advise on the skin. What tells you what caused it is spotting, cast skins or eggs found in the sofa or the bed — and if somebody is being bitten in a living room, underneath the sofa is where to start looking.

Caversham: What To Say When You Book

• That the bites are happening in the evening or during the day, not only overnight
• Which seat, and which end of it
• Whether anybody has been sleeping downstairs, and for how long
• Whether the bedrooms are also producing bites
• Anything found underneath the sofa

Those five answers are usually enough to say whether this is a living room job, a bedroom job that has spread, or a household where somebody moved downstairs and took it with them.