The five roaches you will actually meet
Of the roughly 4,000 cockroach species worldwide, only a handful regularly enter US homes. The University of California's statewide IPM program lists five as common household pests: German, brownbanded, Oriental, American and Turkestan. Three of them account for nearly every infestation most homeowners will see. The table below is the fastest way to narrow it down before you treat anything.
| Species | Adult size | What you see | Where it lives |
|---|---|---|---|
| German (Blattella germanica) | ½ inch | Light brown, two dark stripes on the shield behind the head | Indoors only: kitchens, bathrooms, appliances, warm and humid |
| Brownbanded (Supella longipalpa) | ½ inch | Males golden tan, females darker; light bands across the abdomen, wings and sides | Indoors only, but warmer — around 80°F: electronics, wall art, furniture legs |
| American (Periplaneta americana) | 1½–2 inches | Reddish-brown, pale yellow edge on the shield behind the head | Sewers, drains, steam tunnels, water meter boxes; enters at night |
| Oriental (Blatta orientalis) | About 1¼ inches | Shiny dark brown to almost black; wings short (male) or barely formed (female) | Cool, damp spots: basements, crawlspaces, floor drains, garages |
| Turkestan (Blatta lateralis) | About 1 inch | Cream-colored markings behind the head and around short rounded wings; males yellowish-tan | Outdoors: water meter boxes, concrete cracks, compost, potted plants, sewers |
Not sure which one you have? The Pest ID Wizard walks through size, color, and location in under a minute. The University of California's cockroach pest note has close-up photos of every species for a second opinion.
Indoor breeders and outdoor invaders are two different jobs
The single most useful split in cockroach control is not size or color — it is whether the species is breeding inside your building or walking in from outside. UC IPM draws the line explicitly: German and brownbanded cockroaches live and breed entirely indoors, while American, Oriental and Turkestan cockroaches live outdoors and invade temporarily.
That one sentence changes the whole plan. An indoor breeder means there is a population with egg cases somewhere in the structure, and the job is to reach it. An outdoor invader means the population is somewhere else — a sewer, a water meter box, a compost pile, a damp crawlspace — and the job is to close the route and treat the source. Spraying the baseboards of a kitchen to stop American roaches that are breeding in a storm drain is the classic wasted treatment: the population is untouched and the survivors keep coming.
The practical test is where you see them and when. Roaches on a kitchen counter after dark, in a building with shared walls, point indoors. Roaches in a basement laundry room, a ground-floor bathroom, or a garage — especially large ones — usually point outdoors, and often to moisture.
German cockroach: the indoor specialist
The German cockroach is the most common indoor species in the US — and the most persistent. It lives and breeds entirely inside buildings, prefers warm (70–75°F), humid areas near food and water, and can hide in a crack just 1/16 of an inch wide. That is why it survives in spotless kitchens: it does not need visible crumbs, just the residue behind a refrigerator or under a dishwasher.
Its biology is the reason German roach infestations explode so fast. The female carries a pale beige egg case about 1/4 inch long, and drops it only one to two days before it hatches — sometimes the eggs hatch while she is still carrying it. Each case holds roughly 30 young, and a new case is produced every few weeks. UC IPM estimates that a single female and her offspring can produce over 30,000 individuals in a year, the fastest reproductive cycle of the common pest cockroaches. If you see small roaches with two dark stripes behind the head, you are almost certainly dealing with this species, and the complete roach elimination guide is the playbook to follow: sanitation, gel bait, an IGR, and monitoring.
Brownbanded cockroach: the one in the living room
The brownbanded cockroach is the exception that catches people out, because it is the indoor breeder that is not usually in the kitchen. UC IPM puts it at about 1% of indoor infestations, prefers roughly 80°F — five to ten degrees warmer than a German cockroach likes — and harbors in places a German roach ignores: crevices in or near electrical appliances, behind wall art and decorations, inside the hollow legs of furniture, and in accumulated clutter.
Its diet is different too. Brownbanded roaches prefer starchy material, and the classic example from UC IPM is the glue on stamps and envelopes. That is why a brownbanded problem can look like no problem at all until someone opens a picture frame or moves a bedside table.
Two details matter for identification. Adult males can fly when disturbed, especially above about 85°F; females cannot fly at all. And the female glues her light brown egg case — about 1/4 inch long — to ceilings, the undersides of furniture, or closet surfaces, sometimes several together, where it incubates for several weeks. A female and her offspring can produce over 600 roaches in a year. If you are finding roaches in living rooms, bedrooms and home offices rather than kitchens and bathrooms, suspect brownbanded, and read the treatment matrix below before you buy bait: UC IPM singles this species out as especially difficult to control with baits.
American cockroach: the sewer visitor
The American cockroach is the giant of the group — adults reach 1½ to 2 inches — and it is an outdoor species that invades. It prefers warm, humid conditions above roughly 82°F and thrives in sewers, storm drains, steam tunnels, water meter boxes and damaged drain lines, typically entering homes at night through gaps around pipes, doors and foundation cracks. Seeing one in a basement or ground-floor bathroom is often the first sign of a moisture or entry-point problem, not a breeding colony inside the house.
There is a hygiene reason not to shrug them off. UC IPM notes that because American cockroaches may contact human excrement in sewers or pet droppings outdoors, they can carry bacteria that cause food poisoning, including Salmonella and Shigella. A roach that walked out of a drain and across a counter is worth taking seriously even when it is a single insect.
Reproduction is slower than the German roach but still substantial: the female carries the egg case — about 3/8 inch long, brown when laid and black within a day or two — for roughly six days, then cements it to a protected surface where it incubates for about two months or longer. Each case holds about 12 young, and a female plus her offspring can produce over 800 roaches in a year. Because it does not breed indoors the way German roaches do, the treatment is different: exclusion and source control first. Seal pipe penetrations, install door sweeps, fix leaky drains, and treat outdoor harborages like water meter boxes with bait. The DIY vs Pro calculator can help you decide whether the entry-point work is worth doing yourself.
Oriental cockroach: the damp basement dweller
The Oriental cockroach is shiny, nearly black, and slow-moving — often called the "water bug" or "black beetle roach." It prefers cool, damp environments: garages, basements, crawlspaces, floor drains, water meter boxes, and the area under refrigerators with condensation pans. It is most likely in single-family homes surrounded by vegetation, woodpiles, ivy and ground cover, and it is common anywhere people feed pets or wildlife outdoors.
Two physical limits give it away. Oriental roaches do not fly, and they cannot climb smooth vertical surfaces — which is why they turn up trapped in porcelain sinks and bathtubs, having fallen in or climbed up through a damaged drain pipe. If a roach is stuck in a tub, that is a strong hint you are dealing with this species rather than a German roach.
An Oriental roach problem is almost always a moisture problem. Females deposit dark red-brown egg cases about 3/8 inch long in sheltered debris; a female and her offspring can produce nearly 200 roaches in a year, and development from newly hatched nymph to adult can take one to two years or more. Fixing the humidity — repairing leaks, ventilating crawlspaces, sealing floor drains — matters more than any insecticide. Boric acid dust in wall voids and under appliances works well because the species stays low and close to damp surfaces.
Turkestan cockroach: the newer invader
The Turkestan cockroach is the one most homeowners have never heard of and increasingly likely to meet. UC IPM describes it as a newer invasive species, usually found outdoors in water meter boxes, cracks between poured concrete, compost piles, leaf litter, potted plants and sewer systems. It is also sold online and reared as food for insect-eating pets, which is one route it travels.
Identification is where people go wrong. Females are routinely confused with Oriental cockroaches; the difference is the cream-colored markings along the edges behind the head and around the short, rounded wings, and the reddish head, thorax and legs on the nymphs. Males can be mistaken for small American cockroaches, but they are smaller with yellowish-beige wings edged in cream.
The biology tracks the Oriental roach, with one important difference: Turkestan females mature faster and produce more eggs over their lifetime, and in recent years the species has been displacing Oriental cockroaches in southern California, the Central Valley and other warm, dry parts of the country. If you are in a warm climate and seeing "Oriental" roaches that seem to be everywhere at once, check the markings before assuming.
Reproduction, side by side
Breeding rate is what separates a nuisance from an infestation. The figures below are the UC IPM values for each species, and the spread is almost two orders of magnitude between the German cockroach and the Oriental cockroach.
| Species | Egg case | Young per case | Female + offspring, one year | Egg to adult |
|---|---|---|---|---|
| German | About 1/4 inch, carried until 1–2 days before hatching | About 30 | Over 30,000 | A few months — the fastest of the group |
| Brownbanded | About 1/4 inch, glued to ceilings and furniture | Not specified by UC IPM; several weeks of incubation | Over 600 | Weeks to months |
| American | About 3/8 inch, cemented after about 6 days | About 12 | Over 800 | Months; egg incubation about 2 months or longer |
| Oriental | About 3/8 inch, deposited in sheltered debris | Not specified by UC IPM | Nearly 200 | 1 to 2 years or more |
| Turkestan | Similar to Oriental | More over a lifetime than Oriental | Higher than Oriental — faster maturity | Faster than Oriental |
Two of those cells are deliberately vague, because the published source does not give the number. Filling them with invented figures would make the table look complete and the page less trustworthy. If you want to model the growth rate for your own sighting, the roach reproduction calculator uses the documented per-species values.
Why the species changes the bait
Treating the wrong species is the most common reason roach treatments fail. The first move, the product class and the thing that will not work all change with the identification.
| Species | First move | Product note | What will not work |
|---|---|---|---|
| German | Find the harborage — behind and under appliances — and bait it | Gel bait plus an IGR, with sanitation, repeated over 4–8 weeks | Spraying baseboards; it scatters them deeper into walls |
| Brownbanded | Treat furniture, electronics, wall art and closets | Baits plus dusts in voids — expect this species to be harder to reach with bait | Kitchen-only treatment; the population is elsewhere |
| American | Exclusion and source treatment: seals, sweeps, drains, meter boxes | Bait outdoors in harborages; indoor bait as backup | Fogging — they are not breeding inside |
| Oriental | Correct the moisture: leaks, crawlspace ventilation, floor drains | Boric acid and desiccant dusts in voids and under appliances | Gel bait alone in cool, damp areas — it performs poorly there |
| Turkestan | Treat the outdoor harborage: meter boxes, concrete cracks, compost | Bait and residual treatment where the species actually lives | Indoor-only treatment — the colony is outside |
UC IPM's general rule holds across all five: baits outperform sprays, and pesticides alone will not solve a cockroach problem — sanitation and exclusion are the foundation. Removing other food and water sources makes baits work better, because a roach that has an easy meal is less likely to take the bait.
Why foggers and sprays make the problem worse
Foggers — "bug bombs" — are the most common DIY mistake, and the official guidance is blunt. UC IPM advises avoiding foggers, bombs and aerosol sprays: they can be hazardous, and they may repel and disperse cockroaches to other areas without actually killing them. Dispersal is the opposite of what you want. A German roach population pushed out of a kitchen and into adjacent units or wall voids is harder to treat than the one you started with.
There is a health angle too. The Centers for Disease Control and Prevention lists cockroaches among the common asthma triggers and advises avoiding sprays and foggers specifically because they can cause asthma attacks. Cockroach allergen levels track both population density and the conditions that allow heavy infestations, so the sanitation and exclusion work is not just housekeeping — it is the part that lowers exposure.
What actually works is slower than a fogger and more reliable: bait placed where the roaches are, dusts in undisturbed voids, and enough patience to let the population cycle down. UC IPM's own expectation is that an effective bait program may take seven days or longer before you see fewer roaches — and females carrying egg cases feed very little and avoid open spaces, so they are less likely to be affected early. Judging a bait job at day three is judging it before it has had a chance to work.
How to confirm which one you have
Sticky traps are the honest way to find out, and UC IPM recommends them for exactly this purpose — catching roaches for identification and telling you where the population is concentrated. Place them on the floor along the edges of walls, in cupboards, under appliances, and near exterior doors to catch invading outdoor species. Roaches travel along edges, so a trap flat in the middle of a room catches far less than one against a baseboard. Check them daily until you can tell where most of the catch is coming from.
Then match what you caught against the tables above or run the Pest ID Wizard. One more identification note: nymphs are usually the most abundant stage in a field population, and they do not look like the adults in any guide. If most of your catch is small and wingless, you are looking at an active breeding population rather than a few wandering adults.
If you are seeing roaches in daylight, that is a population signal worth taking seriously: German roach populations that outgrow their hiding spots start moving during the day, and the allergen load they produce is a documented asthma risk factor, especially for children in multi-unit housing. The roach severity quiz turns those sightings into a tier and a next step.
Next steps
Once you know the species, follow the step-by-step roach elimination guide, model how fast the population is growing with the roach reproduction calculator, and compare the cost of DIY versus a professional with the DIY vs Pro calculator. If you are also seeing wood damage, rule out termites with the wood decay vs termite checker before assuming roaches are the whole story.
Species descriptions, sizes, harborage preferences, egg-case details and management guidance on this page follow the University of California Statewide IPM Program's peer-reviewed Pest Notes: Cockroaches (UC ANR Publication 7467). The asthma and spray guidance follows the Centers for Disease Control and Prevention's Controlling Asthma page, which lists cockroaches among common triggers.