The short answer
A bed bug goes through three stages: egg, nymph and adult. Nymphs shed their skin five times as they grow, and need a blood meal before each moult. The British Pest Control Association says adults live for about 10 months, a female can lay 200 to 500 eggs, and bed bugs can survive for months without feeding.
Understanding how bed bugs grow explains a lot about why they are hard to get rid of: why one treatment is often not enough, why the eggs matter so much, and why an empty room can still have bed bugs months later.
The figures below come from the British Pest Control Association (BPCA) unless we say otherwise.
The three stages
Bed bugs do not have a caterpillar or pupa stage. They hatch looking like small, pale versions of the adult and grow in steps.
1. Eggs
Eggs are tiny, white and laid in cracks, seams and crevices close to where people sleep, glued in place so they do not fall out when a mattress is moved. The BPCA says a single female can lay between 200 and 500 eggs in her lifetime. Eggs are the hardest stage to kill: tucked into seams, they are easily missed by sprays, and in laboratory tests they needed higher temperatures, or far longer at a lower temperature, than adults to die.
2. Nymphs
A newly hatched bed bug is called a nymph. It is pale, almost see-through before it feeds, and much smaller than an adult, which makes it easy to miss.
Nymphs grow through five stages. Between each one they shed their skin, and before each moult they need a blood meal. Those shed skins, pale and empty, are one of the signs of bed bugs people find along mattress seams.
3. Adults
After the fifth moult the bed bug is an adult: flat, oval, reddish brown and about 4 to 6mm long. The NHS compares the colour to yellow, red or brown. Adults feed every so often, mate and lay eggs, and the cycle starts again.
How long do bed bugs live?
The BPCA gives an adult lifespan of about 10 months. Over that time one female can add hundreds of eggs to an infestation, which is why a few bugs left alone can become a serious problem within months.
How quickly each generation develops depends mainly on temperature and on how easily the bugs can feed. A warm, occupied bedroom suits them; a cold, empty one slows everything down without stopping it.
How long can bed bugs live without feeding?
For months. The BPCA says bed bugs can go a long time without a blood meal. This is why:
- a flat that has been empty between tenants can still have bed bugs;
- moving out for a few weeks does not starve them out;
- second-hand furniture and luggage can carry live bugs a long way.
What bed bugs can survive
The BPCA says bed bugs can survive temperatures from around freezing up to the high forties in Celsius. They are not killed by a cold spell, a hot day or normal heating. At the top end, though, they have little margin, and that is what heat treatment exploits. Our guide to what temperature kills bed bugs has the figures.
| Stage | What it looks like | What it needs | What kills it |
|---|---|---|---|
| Egg | Tiny, white, glued in seams | Time and warmth to hatch | Heat held long enough; freezing for weeks |
| Nymph (five stages) | Small, pale, darker after feeding | A blood meal before each moult | Heat, professional insecticide |
| Adult | Flat, oval, reddish brown, 4 to 6mm | Occasional blood meals | Heat, professional insecticide |
Why the life cycle matters for treatment
Why sprays often need repeat visits
An insecticide treatment may kill the adults and nymphs it reaches, but eggs can survive and hatch afterwards. That is why spray treatments usually involve two or three visits, timed so that newly hatched nymphs are caught before they grow up and lay eggs of their own.
Why heat can work in one visit
Heat treatment kills all three stages at once, provided the heat reaches every hiding place and is held long enough. That is its main advantage over spraying. It leaves nothing behind to deal with bugs brought back in later, so many firms book a follow-up check.
Why DIY rarely works
Killing the bugs you can see does nothing about the eggs and nymphs you cannot. The BPCA says amateur pesticides are very unlikely to clear an infestation and can spread it to other rooms. The NHS also says getting rid of bed bugs yourself is very hard.
Do bed bugs spread disease?
According to the BPCA, bed bugs have not been shown to spread disease to people. The main problems are bites, itching and lost sleep. Our guide to bed bug bites sets out the NHS advice.
Breaking the cycle
The cycle only stops when every stage is dealt with, in every room where the bugs are. If you have found signs, a specialist survey is the best next step. Our cost calculator shows what heat treatment usually costs, and the form below finds a specialist who covers your area.
Where our information comes from
- British Pest Control Association: bed bugs, how to get rid of them (read 26 October 2026)
- British Pest Control Association: Code of Best Practice for Bed Bug Management and Control (December 2020)
- NHS: Bedbugs (reviewed 1 May 2026)
- Kells and Goblirsch (2011), Temperature and time requirements for controlling bed bugs under commercial heat treatment conditions, Insects 2(3)