Stages: egg (1 mm), five nymphs (1.5–4.5 mm) and adult (5–7 mm) (EPA). Egg to adult: about 38–53 days at 23 °C and 57–76 days at 21 °C (Johnson 1941); Virginia Tech gives about 37 days above 72 °F. Each moult needs a blood meal. No larvae or pupae — bed bugs have incomplete metamorphosis.
Bed bug life cycle: egg, 5 nymph stages, adult
The bed bug life cycle has seven steps: an egg, five nymph stages and the adult. There is no worm-like larva and no pupa — a newly hatched bed bug already looks like a tiny, pale adult, and it grows by shedding its skin (moulting) five times (Johnson 1941; Virginia Tech). The rule that drives the whole bed bug cycle: every nymph must take a blood meal before it can moult, and adult females need blood to lay eggs.
- Egg — about 1 mm, pearl-white, laid in cracks and seams near where people rest. It hatches in about 9.1 days at 23 °C.
- Nymph 1 to Nymph 5 — 1.5 mm growing to 4.5 mm (EPA). Each takes a blood meal, digests it and moults into the next stage. At 23 °C each stage takes about 5–8 days from feeding to moulting.
- Adult — 5–7 mm, about the size of an apple seed (EPA). Adults mate, and females lay eggs after each blood meal for the rest of their months-long lives.
Those are the stages of bed bugs, sometimes listed as the bed bug stages of life or the different stages of bed bugs. Because they grow through these bed bug growth stages by feeding and moulting, the bed bug growth cycle speeds up when hosts are close by and stalls when they aren't. Virginia Tech notes that a nymph with no host "will stay in that current instar until it is able to find a blood meal, or it dies".
Bed bug nymph stages and instars
Entomologists call each nymph stage an instar, so the bed bug instars are the same five bed bug nymph stages. Each needs at least one full meal to moult; several small meals can make an instar last longer (Kemper 1931, quoted by Johnson). How long each instar takes from feeding to moulting:
| Instar | 18 °C (64 °F) | 23 °C (73 °F) | 28 °C (82 °F) |
|---|---|---|---|
| 1st-stage nymph | 11 days | 5.2 days | 2.7 days |
| 2nd-stage nymph | 12 days | 5.3 days | 2.5 days |
| 3rd-stage nymph | 13 days | 5.3 days | 2.5 days |
| 4th-stage nymph | 13 days | 5.3 days | 2.7 days |
| 5th-stage nymph | 16 days | 7.8 days | 3.7 days |
Virginia Tech gives similar room-temperature figures for modern bugs: most nymphs moult within about 5 days of a meal and stay 5–8 days in each instar if they can feed soon after moulting, and 2–3 days longer at 50–60 °F.
The reproductive cycle of bed bugs
The reproductive cycle of bed bugs runs on blood. After a meal, a mated female at 23 °C starts laying on the 5th or 6th day and keeps laying for 8–10 days (Johnson 1941); Virginia Tech gives 1–7 eggs a day for about 10 days after one meal, or 5–20 eggs per meal. She then needs another meal to keep going. Males mate by piercing the female's body wall, and Virginia Tech notes that a single mated female can start an infestation on her own as long as she can feed. Below about 13 °C females stop laying (Johnson 1941). How many eggs does a bed bug lay over a lifetime? About 140 in modern Virginia strains (Virginia Tech) — our bed bug egg page covers eggs in detail.
Stages of bed bugs: actual size of each stage
Here is every stage at its real length from the EPA, drawn to the same scale. It answers the actual size bed bug life cycle question better than a photo can, because photos are rarely to scale. Instead of bed bug life cycle photos, we use original illustrations — this is our life cycle of a bed bug image, with a millimetre ruler so you can compare.
| Stage | Length | Colour | Moults left | Time at 23 °C |
|---|---|---|---|---|
| Egg | 1 mm | pearl-white; an eye spot shows after about 5 days | 5 | 9.1 days to hatch |
| 1st-stage nymph | 1.5 mm | translucent, whitish-yellow; nearly invisible until fed | 5 | 5.2 days |
| 2nd-stage nymph | 2 mm | translucent, whitish-yellow to pale tan | 4 | 5.3 days |
| 3rd-stage nymph | 2.5 mm | pale tan; turns red when fed | 3 | 5.3 days |
| 4th-stage nymph | 3 mm | tan to light brown | 2 | 5.3 days |
| 5th-stage nymph | 4.5 mm | light brown, adult-like but paler | 1 | 7.8 days |
| Adult | 5–7 mm | brown, flat and oval when unfed; reddish-brown and swollen after feeding | — | — |
Bed bug size chart and nymph size
The bed bug size chart above shows how small the early stages are: a first-stage nymph is 1.5 mm and, unfed, "can be nearly invisible to the naked eye" because it is translucent and whitish-yellow (EPA). The bed bug nymph size climbs to 2, 2.5, 3 and finally 4.5 mm before the moult to adult. After a meal any stage swells and turns red, so a fed nymph can look bigger and darker than its stage suggests. The CDC gives the overall range as 1–7 mm.
Baby bed bugs
"Baby bed bugs" are simply the nymphs. They feed on the same blood as adults, bite in the same way, and are easiest to spot right after feeding, when they turn bright red. Finding pale, tiny nymphs means bed bugs are breeding where you found them. If you're unsure what you've found, use the Which stage is this? mode above — and ask a local extension service or pest professional to confirm, because bat bugs and some other insects look very similar.
Life cycle of bed bugs in days
Temperature sets the pace. Johnson (1941) measured every stage at constant temperatures from 15 to 34.5 °C; this is the life cycle of bed bugs in days using his figures:
| Temperature | Egg | Five nymph stages (feeding to moulting) | Egg to adult | Egg to first new eggs | Generations a year |
|---|---|---|---|---|---|
| 15 °C (59 °F) | 35 days | 119 days | 154–204 days | 178–238 days | 1.5–2.1 |
| 18 °C (64.4 °F) | 20 days | 66 days | 86–111 days | 95–125 days | 2.9–3.8 |
| 21 °C (69.8 °F) | 14 days | 44 days | 57–76 days | 64–87 days | 4.2–5.7 |
| 23 °C (73.4 °F) | 9.1 days | 29 days | 38–53 days | 43–61 days | 5.9–8.4 |
| 25 °C (77 °F) | 7.7 days | 24 days | 32–42 days | 35–47 days | 7.8–10.6 |
| 28 °C (82.4 °F) | 5.7 days | 14 days | 20–30 days | 22–34 days | 10.6–16.2 |
| 34.5 °C (94.1 °F) | 4.5 days | 15 days | 20–30 days | 23–35 days | 10.6–16.2 |
The shorter figure in each range assumes nymphs feed as soon as they're able, which is what Johnson saw when bed bugs lived beside a mouse; the longer one adds his allowance for finding a host — 2 days per meal at 25–28 °C, 3 at 23 °C, 5 at 18 °C and 10 at 15 °C. Below 18 °C Johnson called prediction "impossible at present", because nymphs kept cool before feeding often failed to moult.
So the life cycle of a bed bug in days at a typical 21 °C is about 57–76 days from egg to adult. For comparison, Virginia Tech gives about 37 days at temperatures above 72 °F, and a 2011 life table at 26 °C measured 34.8–40.4 days (Polanco, Brewster & Miller). For your own life cycle of bed bugs timeline with dates, use the calculator above.
Bed bug life cycle: how long from egg to egg?
Bed bug life cycle how long? A full turn — egg to an adult laying its own eggs — takes about 43–61 days at 23 °C and 30–42 days at 26 °C. Whether you search how long bed bug life cycle, how long is bed bug life cycle or how long is life cycle of bed bug, that egg-to-egg time is what sets how fast an infestation grows. After that, adults live for months: see the bed bug lifespan calculator.
The egg stage in brief
The egg stage is part of every total above: about 14 days at 21 °C, under a week above 27 °C, and no hatching at all below 13 °C or at 37 °C (Johnson 1941). For hatch dates, how long eggs survive and what they look like, use the bed bug egg hatch timer.
Bed bug larvae and pupae? Why bed bugs don't have them
People often search for larvae of bed bugs or a bed bug pupa, but bed bugs have neither. They are true bugs (order Hemiptera) with incomplete metamorphosis: the young (nymphs) look like small adults, live in the same places and eat the same food, and change gradually with each moult. There is no grub-like larva and no resting pupa stage, unlike flies, beetles or fleas, which go egg → larva → pupa → adult.
If you've found a small, worm-like or cocoon-like thing near your bed, it isn't a bed bug stage. Things often mistaken for them include:
- Shed nymph skins — pale, hollow, bed-bug-shaped casings left after a moult. These are bed bug evidence.
- Flea larvae — tiny, worm-like and bristly, found in pet bedding and carpets. Fleas do have larvae and pupae; see our flea and gnat identifier.
- Carpet beetle larvae — fuzzy, banded grubs that feed on fabrics.
How long does it take bed bugs to grow and multiply?
How long does it take bed bugs to grow from egg to adult? About 38–53 days at 23 °C, as long as each nymph finds a meal. They can't speed past that — each moult needs a meal and digestion time — but warmth helps: at 28 °C it's about 20–30 days.
How fast do bed bugs multiply?
How fast do bed bugs multiply? Faster than most people expect, but slower than flies:
- A 2011 life table at 26 °C measured a population doubling time of about 13 days, a mean generation time of 91.5 days, and a net reproductive rate of about 35 daughters per female (Polanco, Brewster & Miller).
- Virginia Tech says that at 70–90 °F with a host present, a population "can double every 16 days".
- More than 80% of eggs survive to become breeding adults under good conditions (Virginia Tech).
Doubling every two weeks means a handful of bugs can become hundreds within a few months. Cooler rooms slow this sharply, because both development and egg-laying slow down.
How long until bed bugs appear after you bring them home?
How long does it take for bed bug to appear after they arrive in luggage or furniture? It depends on what arrived:
- A fed, mated female: she can lay eggs within days; the first nymphs could hatch about 14 days later at 21 °C, and the first new adults appear after about 57–76 days in total.
- A few nymphs or adults: they start biting within days, but the first bites may not be noticed — marks can take 1 to 14 days to appear, and some people don't react at all (CDC).
- Noticeable numbers: often only after the first new generation, roughly six to nine weeks at room temperature, and longer in cool rooms.
Most bed bugs live within 8 feet of where people sleep (CDC), so that's the first place to check. The calculator above gives dates for your temperature, starting from the day they were likely brought in.
How this life cycle calculator works
- Life cycle timeline: the egg stage comes from Johnson's (1941) Table 2 (eggs hatch from 13 to 35 °C), and each nymph stage from his Table 3 (feeding to moulting at 15–34.5 °C), joined by straight-line interpolation between measured temperatures. Stage dates assume each nymph feeds as soon as it can; the longer egg-to-adult figure adds Johnson's per-meal allowance for finding a host. "New eggs from" adds his feed-to-first-egg time for the new adults. Generations a year is 365 divided by the egg-to-egg time.
- Which stage is this? sizes and colours from the EPA; moults left from the five-instar life cycle; time to adulthood from the same Johnson figures as the timeline.
- Drawings: original illustrations drawn to one scale from EPA lengths, not photos.
Everything comes from the shared bed bug data model on this site, so the egg times match the egg hatch timer and the nymph times match the lifespan calculator. Laboratory bugs had easy access to a host; in a real home development is often slower (Johnson 1941).
Frequently asked questions
What is the bed bug life cycle?
Egg, five nymph stages and adult. Each nymph must take a blood meal to moult to the next stage; adults mate and females lay eggs after each meal (Johnson 1941; Virginia Tech).
How long is the bed bug life cycle?
Egg to adult takes about 38–53 days at 23 °C and egg to the next generation's eggs about 43–61 days (Johnson 1941). Virginia Tech gives about 37 days egg to adult above 72 °F.
How many stages do bed bugs have?
Seven: egg, five nymph stages (instars) and adult.
How big is each bed bug stage?
Egg 1 mm; nymphs 1.5, 2, 2.5, 3 and 4.5 mm; adults 5–7 mm, about the size of an apple seed (EPA).
Do bed bugs have larvae or pupae?
No. Bed bugs have incomplete metamorphosis: nymphs look like small adults and there's no larva or pupa stage.
What do baby bed bugs look like?
Tiny (1.5–4.5 mm), translucent or whitish-yellow nymphs that turn red after feeding. Unfed first-stage nymphs can be nearly invisible (EPA).
How long does it take bed bugs to grow?
About 57–76 days from egg to adult at 21 °C, if each nymph can feed. Without a meal, a nymph can't moult at all.
How fast do bed bugs multiply?
A 2011 life table at 26 °C measured a doubling time of about 13 days (Polanco et al.); Virginia Tech says about every 16 days under good conditions.
How many generations of bed bugs are there a year?
About 5.9–8.4 at 23 °C based on Johnson's egg-to-egg times; fewer in cool rooms.
How long until bed bugs appear after bringing them home?
Bites can start within days, but marks may take up to 14 days to show (CDC) and noticeable numbers often take six to nine weeks at room temperature.
Does temperature change the bed bug life cycle?
Yes, strongly. Egg to adult takes about 3 weeks at 28 °C but around 3 months at 18 °C, and below 13 °C eggs don't hatch and first-stage nymphs don't moult (Johnson 1941).
Are bed bug nymphs and instars the same thing?
Yes. Each of the five nymph stages is called an instar; a nymph moves to the next instar each time it moults.
Can a single bed bug start an infestation?
A single mated female can, as long as she can feed regularly (Virginia Tech).
These calculators give estimates from laboratory studies, for education. Real bed bugs vary with strain, insecticide resistance, humidity and how easily they reach a host. Bed bugs are not known to spread disease (CDC), but if bites trouble you, talk to a doctor or pharmacist. For an infestation, contact a licensed pest professional or your local extension service. We give no pesticide advice.