Cockroaches: Identification, Health Risks and Control

What does a cockroach look like?

A cockroach is a flat-bodied insect with long, thin antennae, spiny legs built for running, and a shield-like plate called the pronotum that hides its head when you look down on it. Texas A&M AgriLife Extension's cockroach guide describes them that way and adds that cockroaches may be brown, black, tan, reddish orange or pale green. Most have wings, though in some species the wings are short and do not work. The adults found around US homes run from about 1/2 inch to 2 inches long, depending on the species.

Young cockroaches, called nymphs, look like smaller, wingless adults. The University of California's Pest Notes on cockroaches explains that nymphs grow by gradual metamorphosis: they eat what adults eat and resemble them, but lack fully developed wings and cannot reproduce. A cockroach that has just molted is white and darkens as its new covering hardens, usually within hours, so a pure white roach is a freshly molted one and not a separate kind. Because nymphs are typically the most abundant stage in a population, knowing what baby cockroaches look like in each species is as useful as knowing the adults.

Eggs come packaged in a small, brown, bean-shaped case called an ootheca. UC IPM advises looking for egg cases glued to the undersides of furniture and tucked into appliance motors and boxes, especially on items being brought into the home, and removing any you find.

Plenty of dark, fast insects are not cockroaches at all. UC IPM notes that some people confuse cockroaches with beetles, and that adult cockroaches lack the thick, hardened front wings a beetle has. A separate guide compares the bugs that look like cockroaches and gives the features that separate each one from a pest roach.

Which cockroaches are found in US homes, and how do you tell them apart?

The cockroaches a US household is most likely to meet fall into three groups: two that live indoors (German and brown-banded), four that live mostly outdoors or in sewers and come inside for food or water (American, Oriental, smokybrown and Turkestan), and wood roaches that wander in but cannot survive indoors. The group matters more than the exact species, because indoor breeders are treated with bait where they hide, while outdoor species are mainly a sealing and moisture problem. Size, color and the markings on the pronotum separate them.

German cockroach

The German cockroach (Blattella germanica) is the small, light brown roach of kitchens and bathrooms: 1/2 to 5/8 inch (13 to 16 mm) long, with two dark parallel stripes on the plate behind its head, according to Rutgers University's German cockroach fact sheet. Texas A&M notes that both sexes have wings reaching the end of the abdomen but do not fly, and calls it the most prolific of the indoor cockroaches. It adds that two outdoor relatives, the Asian (Blattella asahinai) and field (Blattella vaga) cockroaches, look very similar, so a striped roach found only in the yard may not be a German cockroach at all. Identification details, hiding places and the full control program are in the German cockroach guide.

Brown-banded cockroach

The brown-banded cockroach (Supella longipalpa) is about the size of a German cockroach but lacks the two lengthwise stripes; it has two yellowish bands running across the wings instead. The University of Kentucky's cockroach fact sheet describes it as far less common than the German cockroach and as a roach of the whole house, not only the kitchen: high on walls and in upper cabinets and closets, behind picture frames, and under or inside furniture, where females glue pea-sized egg capsules to hidden surfaces. UC IPM adds that it prefers temperatures around 80°F, hides in and near electrical appliances, and is especially difficult to control with baits.

American cockroach

The American cockroach (Periplaneta americana) is the largest common species at 1 1/2 to 2 inches long, reddish brown with a tan to light yellow band outlining the pronotum. Texas A&M says it is also known as the waterbug or palmetto bug and is one of the most common cockroaches in sewer systems. Indoors it keeps to dark, moist places; Kentucky lists basements, crawl spaces, floor drains, sump pumps, pipe chases, laundry areas, boiler rooms and steam tunnels. By Texas A&M's account it is slow to mature, reaching adulthood in an average of 600 days, and adults usually live 1 to 2 years. The waterbug nickname causes enough confusion that a separate page sorts out water bugs versus cockroaches.

Oriental cockroach

The Oriental cockroach (Blatta orientalis) is a shiny, dark brown to black roach about 1 to 1 1/4 inches long that UC IPM says is sometimes called a water bug or black beetle. Kentucky describes the males' wings as covering about half the abdomen and the females' as very short; neither sex flies, and UC IPM notes they cannot climb smooth vertical surfaces. They are sluggish, stay at ground level, and prefer cool, dark, damp places such as sewers, crawl spaces, cellars, basements, floor drains and water meter boxes. Development from egg to adult averages 575 to 600 days in Texas A&M's account, and adults live 1 to 6 months.

Smokybrown cockroach

The smokybrown cockroach (Periplaneta fuliginosa) is a dark brown to black roach 1 1/4 to 1 1/2 inches long whose wings extend past the abdomen in both sexes. Texas A&M describes it as common outdoors, especially in the more humid parts of Texas and other southern states, in protected, moist, warm sites such as ground cover, mulch, palm fronds, soffits, attic eaves and tree holes. UC IPM says adults can fly, especially on warm, humid evenings, and that they favor the upper parts of buildings and sometimes take refuge in attics. A large, dark roach that takes flight on a muggy night fits this species, and the guide to which cockroaches can fly compares it with the others.

Turkestan cockroach

The Turkestan cockroach (Blatta lateralis) is a newer invasive species in which the sexes look like two different insects. Males are brownish yellow and 1/2 to 7/8 inch long; females are dark, short-winged and about 1 inch long, and are often mistaken for Oriental cockroaches until you see the cream-colored markings behind the head and around the wings. Texas A&M reports that the species is native to Asia, was introduced to California, and is expanding into Texas, where it has become one of the most common outdoor cockroaches in El Paso. It lives outdoors in water meter boxes, cracks between concrete slabs, compost, leaf litter and potted plants, and UC IPM says it is displacing the Oriental cockroach in the warm, dry parts of California.

Wood roaches

Wood roaches (Parcoblatta species) are outdoor cockroaches about 1 inch long, brownish, and in some species edged in white along the outer wing margin. The University of Kentucky says they live beneath loose bark in woodpiles, fallen logs and dead trees, that the males are excellent fliers, and that both sexes are attracted to lights. They turn up indoors in spring and summer, when large numbers wander in from outside, or in winter on firewood, but they cannot survive indoors. A wood roach in the living room is a nuisance, not an infestation.

How fast do cockroaches multiply?

The German cockroach multiplies fastest by a wide margin: by Rutgers' figures an egg case holds about 40 eggs, a female produces 5 to 8 cases, and the whole life cycle takes about 100 days. Texas A&M puts the yield of one case at 30 to 40 nymphs and UC IPM at about 30 young. UC IPM estimates that a single female and her offspring can produce over 30,000 individuals in a year. The large outdoor species are far slower, which is why German cockroaches, not the big roaches, are behind the infestations that seem to explode.

All cockroaches pass through three stages: egg, nymph and adult. How the egg case is handled differs by species. UC IPM explains that a German cockroach female carries her egg case for most of its roughly 30-day incubation and drops it about when the eggs hatch, while other species carry theirs only briefly before leaving it in a sheltered spot to incubate for weeks or months. It also notes that females carrying egg cases feed very little and avoid open spaces, so bait is slower to reach them. Rutgers adds that German cockroach nymphs molt 5 to 6 times, and that females live 140 to 280 days and males 90 to 140 days.

Warmth speeds everything up. Texas A&M puts the German cockroach's optimum near 80°F and says a nymph takes 50 to 60 days to become an adult at average indoor temperatures; Rutgers notes that below 59°F (15°C) cockroaches survive but nymphs stop developing into adults. Roaches congregate near sources of heat and moisture, Texas A&M notes, and Rutgers reports that the areas around the stove and refrigerator usually hold the largest numbers.

Most of the population stays out of sight. Texas A&M reports that a German cockroach spends about 75 percent of its life in narrow cracks 1/32 to 3/16 inch wide, and Rutgers says an actively growing population is about 80 percent nymphs and 20 percent adults. Kentucky adds that cockroaches gather in particular spots in response to aggregating odors in their feces. The few adults you see at night are a small sample of what is living in the cabinets and wall voids.

Where do cockroaches come from?

Cockroaches reach a home by four routes: carried in with belongings, through shared walls and plumbing, up through drains, or in from the yard. Which route applies depends on the species, and the detailed guide to where cockroaches come from covers how to close each one.

• Carried in. German cockroaches are often introduced in infested grocery bags, beverage cartons or furniture, according to the University of Kentucky. UC IPM says to check appliances, furniture, boxes and anything that was recently in storage.
• Through the building. Kentucky notes that German cockroaches often travel between rooms and adjoining apartments through walls, ceilings, pipes and wiring.
• Up from drains. Texas A&M identifies floor drains as a common entry point for American and Oriental cockroaches, both of which live in sewers and other wet, below-ground spaces.
• In from outdoors. The Kentucky and Texas A&M fact sheets between them describe American, Oriental, smokybrown and wood cockroaches coming in through gaps around doors, windows, vents and utility openings, through poorly sealed roof soffits, and on firewood.

A clean house is not immune. The University of Kentucky fact sheet says that roaches usually thrive where sanitation is poor but that even clean homes can become infested, because of the ways roaches get in: carried in with infested items, or through shared walls and ceilings.

What are the signs of a cockroach infestation?

The clearest signs are droppings that look like ground pepper, dark fecal spots or smears, shed skins, egg cases, and live or dead cockroaches. UC IPM uses the spots, skins, egg cases and the insects themselves as its markers for where roaches are active, and Texas A&M describes the droppings as looking like crushed pepper and sticking to surfaces where roaches congregate. Check with a bright flashlight in the places they hide: cabinet corners, under sinks, behind the refrigerator and stove, and around the water heater.

Daytime sightings are a bad sign. Cockroaches hide by day and come out at night to feed, so Texas A&M's rule of thumb is that seeing them during the day usually means there are a lot of them. A single large roach near a door or floor drain is a different situation and may be an outdoor species that wandered in.

Fecal spotting can be confused with other pests. Kentucky notes that it resembles bed bug spotting but can usually be told apart by location, because cockroaches seldom gather on beds the way bed bugs do; the bed bug reference shows what that pest leaves behind. If the droppings come with gnawed packaging or shredded nesting material, compare them against the mouse reference before assuming roaches.

If the evidence is thin, sticky traps settle it. UC IPM says roaches are often caught within the first 24 hours of setting a trap, and the catch tells you both the species and where they are concentrated.

Are cockroaches a health risk?

Yes. Cockroach allergens can trigger allergies and asthma, and the insects can carry microbes onto food. The EPA's guidance on asthma triggers states that droppings and body parts of cockroaches can trigger asthma, that certain proteins in cockroach feces and saliva cause allergic reactions or asthma symptoms in some people, and that cockroach allergens likely play a significant role in asthma in many urban areas. Rutgers names the sources inside a home: feces, shed skins and the bodies of dead cockroaches.

Children in heavily infested housing carry much of that burden. UC IPM reports that indoor infestations have been identified as risk factors for the development of asthma in children, especially in multi-unit housing, and that allergen levels track both cockroach density and the conditions behind heavy infestations, such as housing disrepair and poor sanitation. Kentucky describes the allergic symptoms as congestion, sneezing and watery eyes, and the asthma as recurrent cough, wheezing and difficulty breathing.

Cockroaches also carry microbes from filth to food. UC IPM says German cockroaches are believed capable of transmitting Staphylococcus and Streptococcus bacteria, hepatitis virus and coliform bacteria, and that American cockroaches, which contact sewage and pet droppings, can transmit the Salmonella and Shigella bacteria that cause food poisoning. The wording in these sources is careful, and none of them puts a number on how often a household infestation actually makes someone sick.

Biting is not among the risks these agencies and universities list. None of the fact sheets cited on this page mentions bites, and a separate guide examines whether cockroaches bite.

Killing the roaches does not remove the allergen already in the home. Rutgers recommends a vacuum with a HEPA filter to remove live and dead cockroaches, fecal material and shed skins, and Texas A&M gives the same advice because roach hiding places hold allergens that can cause asthma or make breathing difficult for some people.

How do you keep cockroaches out of your home?

Take away their food, water and hiding places, then close the openings they use. The extension fact sheets cited here all put those steps ahead of any insecticide, and UC IPM states flatly that pesticides alone will not solve a cockroach problem.

• Lock up food. Store food in glass jars or resealable plastic containers, keep garbage in cans with tight-fitting lids, and do not leave unwashed dishes or pet food out overnight.
• Cut off water. Fix plumbing leaks, ventilate areas with condensation, keep mops and wet items off the floor, and empty pet bowls at night.
• Reduce clutter. Throw out stacks of paper bags, cartons and newspapers, or store them in sealed plastic bags.
• Seal the gaps. Caulk cracks around doors and windows, add door sweeps and weather stripping, and close the openings where pipes and wires pass through walls and floors with caulk, foam or copper mesh.
• Inspect what comes in. Look over food deliveries, boxes, secondhand furniture and used appliances before they reach the kitchen.
• Keep drain traps full. Texas A&M advises keeping P-traps filled with water so there is a barrier between the sewer and the building.

Ants exploit the same crumbs and the same gaps, and they have their own complete ant reference.

What should you change outside?

Outdoors, remove the damp, sheltered spots next to the foundation. UC IPM recommends trimming shrubbery to let in light and air, removing ivy and dense ground cover near the house, moving stacked lumber, firewood and trash away from the walls, and considering a gravel strip 6 to 12 inches wide around the building. Texas A&M adds checking the threshold seals under doors and screening roof soffits. Yard cleanup pays off against more than roaches: standing water is the focus of the backyard mosquito control guide, and leaf litter and woodpiles feature in the tick control guide.

What is the right order for getting rid of cockroaches?

Monitor first, clean second, bait third, and use an insect growth regulator or a dust to support the bait, not to replace it. The core of that is the sequence Rutgers lays out: find where the roaches are with sticky traps and inspection, clean daily and cut clutter, apply control products with bait as the preferred method, then re-inspect and re-treat every 2 to 4 weeks until none are seen or trapped for at least a month. A companion page turns the sequence into a step-by-step, bait-first treatment plan, and the cockroach control product guides go deeper on the product types named below.

1. Monitor with sticky traps

Sticky traps tell you which species you have, where it is concentrated and whether treatment is working. UC IPM calls them the best way to detect and monitor cockroaches and says to set them where floors meet walls, behind large appliances, inside cabinets and in the corners of the room, then check daily for several days to find where the catch is highest. In a study of a 188-unit apartment building in New Jersey, traps beside the stove and refrigerator caught significantly more German cockroaches than traps under the kitchen sink or in the bathroom. Traps are a measuring tool: Texas A&M says traps alone do not provide sufficient control of a well-established infestation.

2. Clean, declutter and vacuum

Sanitation makes bait work. UC IPM warns that baits take longer when roaches have other food available and that removing competing food greatly improves results. Texas A&M explains why: when food and water are scarce, roaches must search farther each night, which puts stress on the population. Vacuum crumbs, droppings and the insects themselves from under and behind appliances with a HEPA-filtered machine before you bait.

3. Place gel bait or bait stations

Bait is the main killing tool. Rutgers calls it the most effective formulation and says gel bait usually beats bait stations because it can be put closer to hiding places and is more palatable. The active ingredients named in the Rutgers and UC IPM fact sheets include fipronil, indoxacarb, abamectin, hydramethylnon, dinotefuran, clothianidin, imidacloprid and boric acid.

Placement decides whether it works. Apply gel as many pea-sized dots in and next to hiding places, such as the underside of the kitchen sink, cabinet corners and door hinges, and avoid large globs or lines. Kentucky points out that roaches are not drawn to bait from a distance, so more small placements mean more of them find it; the corners and edges of the cabinets under one kitchen sink can take more than a dozen. As a general rule, Rutgers estimates that a typical one-bedroom apartment may need 10 to 30 grams of gel; the product label sets how much to apply. For stations, Texas A&M says to set at least one within 1 to 2 feet of every suspected hiding place, along a wall or cabinet edge.

Expect a delay, then a steady decline. Kentucky reports that a roach that eats bait typically dies within 1 to 3 days and that a substantial reduction should be apparent within a few weeks; UC IPM says a bait program may take 7 days or longer to show results. Do not spray cleaners or insecticides near bait, because roaches avoid contaminated placements. If the bait has not controlled the population in 2 to 3 weeks, Texas A&M advises switching to one with a different active ingredient, and Rutgers recommends using products from different chemical classes to avoid resistance.

4. Add an insect growth regulator for heavy, chronic infestations

An insect growth regulator (IGR) stops reproduction; it does not kill adult roaches. The National Pesticide Information Center explains that IGRs mimic hormones in young insects and disrupt how they grow and reproduce, that adults usually survive treatment but the eggs they produce may not, and that the class, which includes pyriproxyfen and methoprene, is generally low in toxicity to humans. Rutgers considers IGRs useful only where cockroach numbers are high and chronic, most effective combined with bait, and unable to bring numbers down quickly when used alone. Use only a product whose label lists cockroaches and the indoor site you are treating.

5. Dust hidden voids

Boric acid dust works slowly but lasts as long as it stays dry. Roaches pick it up crossing a treated surface and swallow it while grooming; Kentucky says it keeps its potency almost indefinitely when dry, and UC IPM says it can take 7 days or more to have a significant effect. Apply it as a film barely visible to the eye, because roaches avoid heavy deposits, and only into hidden spaces: the void under cabinets, behind and under the refrigerator, stove and dishwasher, and where plumbing enters walls.

Keep dust off anything people or food touch. Kentucky says never to apply boric acid to countertops or other exposed surfaces, to wipe up stray powder with a damp cloth, and not to puff it into electronics. UC IPM adds that boric acid is toxic to plants and is not recommended outdoors. Diatomaceous earth and silica dusts work by damaging the waxy outer layer of the insect so that it dries out, but Rutgers and Kentucky both rate diatomaceous earth as less effective than boric acid against cockroaches.

Why do sprays and foggers fail against cockroaches?

They put insecticide on open surfaces, and cockroaches live inside cracks. UC IPM says aerosols and total-release foggers are often ineffective because they do not reach the crevices where roaches shelter and breed. Sprays can produce a quick knockdown, but UC IPM says they do not give long-term control, can repel and scatter roaches to other parts of the building, and face resistance to many of the insecticides in common spray cans. Rutgers identifies the usual spray ingredients as pyrethroids (permethrin, cypermethrin, deltamethrin and lambda-cyhalothrin) and describes them as repellent to cockroaches.

The fogger evidence comes from real apartments. In a North Carolina State University field study, researchers set off four commercial fogger products in 20 homes with German cockroach infestations, following the label directions, and found no decline in roach numbers two weeks or one month later. In 10 comparison homes treated with gel bait, the university reports that the baits were effective at eliminating the populations within four weeks; the paper's abstract describes the result as significant declines. Four to six hours after fogging, average insecticide residues on horizontal surfaces were about 600 times the baseline level (the median increase was 85 times), and a month later 34 percent of the swabbed surfaces were still above baseline.

Foggers add a fire risk. Kentucky notes that fogger ingredients may be flammable near an open flame and that injuries and house fires have followed when people did not put out pilot lights, and Rutgers warns of a fire hazard in homes with gas appliances when too many foggers are used.

Gadgets and natural sprays do not close the gap. Rutgers states that no scientific evidence supports the claims made for electronic pest-repelling devices, and that essential-oil sprays are typically effective only when applied directly to the insect and leave little or no residual effect. The wider evidence on plant-based products is covered in what natural pest control can and cannot do.

If you do use a spray, Kentucky's advice is to aim it into the places where roaches hide and at any fecal spotting, not across walls, floors, baseboards and countertops, where they spend very little time.

What is different about cockroaches in apartments?

In a multi-unit building, cockroaches are a building problem, and treating one apartment rarely ends it. Rutgers explains that German cockroaches are more common in apartment buildings because common utilities, shared walls and hallways let them spread from unit to unit. The New Jersey apartment study cited above found that infestations were spatially correlated at the start, meaning infested units clustered together. After 12 months of building-wide integrated pest management, only infestations between floors remained correlated, and the authors concluded that the program reduced movement between units as well as eliminating infestations within them.

Three things follow for a tenant. Report roaches to the property manager early and ask whether neighboring units will be inspected, since a unit-by-unit response can leave the source in place. Seal the openings where plumbing and wiring pass through shared walls; Kentucky singles this out as especially useful in apartments for reducing migration between adjoining units. And skip the spray can: Rutgers warns that pyrethroid sprays may push cockroaches into neighboring units through pipe penetrations and common walls.

Check your lease and your local housing code to see who is responsible for treatment before paying for it yourself.

What should you do about cockroaches that live outdoors?

For American, Oriental, smokybrown and Turkestan cockroaches, work on the entry points and the yard, not the kitchen cabinets. Texas A&M describes the large species as living outdoors and in nonfood areas of buildings and becoming pests when they come inside, and says to look for them in dark, moist places near decaying organic matter: compost piles, ground cover, mulch, hollow trees, old stumps, woodpiles, sewer manholes and underground water meters.

• Find the entry point. Sticky cards next to exterior doors, behind laundry appliances and under stoves and refrigerators show where roaches are traveling, and can catch low numbers of the larger species.
• Close it. Repair door thresholds, screen roof soffits, and keep floor drain traps filled with water.
• Bait outdoors if needed. Texas A&M recommends granular cockroach baits sprinkled lightly in ground cover and mulched beds as the label directs, without leaving visible mounds that could attract dogs or cats, and large-roach bait stations set against walls near doors.
• Find the source of American cockroaches. Kentucky notes that they travel long distances from their aggregation sites and that lasting relief requires finding and treating those areas.

Wood roaches call for exclusion, not indoor treatment, because Kentucky says they cannot survive indoors. They also ride in on firewood in winter, so bring in only what you are about to burn, and keep door sweeps and window screens tight in spring and summer, when large numbers wander in from outside.

When should you call a professional?

Call a licensed pest control professional when the infestation is heavy, when it has not declined after a few weeks of correctly placed bait, or when it involves a shared building. UC IPM says serious indoor infestations and large or complex cockroach problems often require professional service, and Rutgers suggests hiring one if you are not comfortable doing the work yourself, noting that professionals have training, experience and access to more products.

Know what good service looks like. Kentucky says the technician should inspect thoroughly on every visit and apply insecticide into cracks and hidden areas, not along baseboards and other exposed surfaces. It also says eliminating cockroaches should not take a full year when treatment is done correctly, especially in a single-family home, and that once an infestation is gone there is seldom a need to keep reapplying month after month. Some companies offer a limited number of treatments; others require a year of general pest service, so ask before you sign.

Two common do-it-yourself mistakes, according to Rutgers, are relying on sprays as the main method and stopping treatment while small numbers of roaches are still present. For help deciding, see what pest control typically costs and which pest jobs are realistic to do yourself.

This guide is general educational information, not medical advice. If you have symptoms or concerns after a bite or exposure, contact a healthcare provider.

Use any pesticide exactly as its label directs. The label is the law, and what is registered and sold varies by state.

Frequently Asked Questions

Sources

1. Cockroaches (Home and Landscape) — University of California Statewide IPM Program
2. ENTFACT-614: Cockroach Elimination in Homes and Apartments — University of Kentucky Department of Entomology
3. ENTO-037: Cockroach Biology and Management — Texas A&M AgriLife Extension Service
4. FS1322: German Cockroach — Rutgers New Jersey Agricultural Experiment Station
5. Asthma Triggers: Gain Control — US Environmental Protection Agency
6. 'Bug Bombs' Are Ineffective Killing Roaches Indoors — North Carolina State University
7. Spatial Distribution of German Cockroaches in a High-Rise Apartment Building During Building-Wide Integrated Pest Management — Journal of Economic Entomology (Oxford Academic)
8. Insect Growth Regulators (IGRs) — National Pesticide Information Center

How this guide was made: it was researched and drafted with AI assistance from the sources listed above. A second, independent AI pass then checked each factual claim against those sources. Found an error? Email support@buzzskito.ca.