Cockroaches

Cockroaches are flat, fast, night-active insects that live wherever they find warmth, moisture, and food, and in US homes the one that actually breeds indoors is almost always the small German cockroach. The large roaches you see running across a porch or out of a floor drain (American, oriental, smokybrown) are mostly outdoor or sewer insects that wander in.

That difference decides everything: a German cockroach problem needs baiting and patience inside the kitchen and bathroom, while a big-roach problem is usually solved by sealing entry points and fixing moisture.

What a cockroach looks like

All cockroaches share the same basic body plan:

• Flat, oval body that slides into cracks as thin as a coin (1/16 inch for German adults; nymphs hide in even narrower gaps).
• Long, thread-like antennae, often as long as the body.
• Shield over the head (the pronotum), so from above you barely see the head.
• Six spiny legs built for running; roaches can cover about 3 feet per second.
• Two pairs of wings in adults of most species, although many can't truly fly.
• Two short "tail" appendages (cerci) at the rear that sense air movement - that's why they bolt before your hand reaches them.

Nymphs (babies) look like small, wingless adults. See baby cockroaches for how to tell them apart from other small bugs.

The roaches you'll find in US homes

Full comparisons with photos are in types of cockroaches. In the South, people call the large outdoor species "palmetto bugs" or "water bugs."

What do roaches eat?

Cockroaches are scavengers. They eat crumbs and grease, sugar and starch, pet food left in the bowl, garbage, glue in cardboard boxes and wallpaper paste, book bindings, soap film, hair, and dead insects - including other roaches. This is why "I keep a clean house" doesn't guarantee a roach-free house: a film of grease behind the stove or crumbs inside the toaster will feed a colony.

Water is the bigger limit. A German cockroach can go weeks without food but only a few days without water. Leaky P-traps, condensation on pipes, a wet sponge, a pet water bowl, and the drip tray under the fridge all keep roaches alive. Fixing moisture is one of the cheapest things you can do. More on what attracts them: what causes roaches.

Cockroach lifespan: how long do roaches live?

Roaches develop by gradual metamorphosis: egg case (ootheca) → several nymph stages → adult.

Figures from Penn State Extension and UC IPM; numbers vary with temperature.

The German cockroach's advantage is that the female carries her egg case until a day or two before it hatches, so the eggs aren't exposed to treatments or predators, and she starts the next case within a couple of weeks. That is why German roaches go from "saw one" to "they're in the microwave" within a season, while big roaches rarely build up indoors.

Cold slows them down. Roaches from the tropics can't survive a northern winter outdoors, which is why German cockroaches are almost exclusively indoor insects in the US.

Signs of a cockroach infestation

• Droppings: black pepper-like specks (German) or small dark pellets with ridges (American) in drawers, cabinet hinges, and along shelf edges. See roach droppings.
• Smear marks where walls meet the floor in humid areas.
• Egg cases: brown, purse-shaped capsules about 1/4-3/8 inch - see cockroach eggs.
• Shed skins of nymphs near hiding places.
• A musty, oily odor in heavy infestations.
• Roaches in the daytime. They avoid light, so daytime sightings usually mean hiding spots are crowded.

The quickest way to measure a problem: put 4-6 sticky traps overnight under the sink, behind the fridge and stove, and in the bathroom vanity. More than a handful of small brown roaches means an established German cockroach population. See cockroach traps.

Are cockroaches harmful?

Cockroaches are rated as moderately dangerous, mainly because of allergens. Proteins in their droppings, shed skins, and saliva become part of household dust. German cockroaches produce at least 11 airborne allergens; a Purdue study summarizing the research notes that 85% of inner-city US homes test positive for cockroach allergen and 60-93% of inner-city children with asthma are sensitized to it. Penn State lists gastroenteritis-type illnesses (food poisoning, diarrhea) as the main diseases roaches can carry mechanically on legs and bodies. They can also pick up bacteria from drains and garbage and leave them on dishes and counters.

They are not aggressive and bites are rare - see do roaches bite?. Anyone in the household with asthma is a strong reason not to tolerate an infestation for months.

Dead cockroach: what it means

Finding a single dead roach on its back is common after baiting: many insecticides affect the nervous system, the roach loses coordination, and it dies belly up. A big roach dead in the bathtub in summer often came in from outside. Several dead small roaches out in the open, though, mean there's an indoor population. Sweep up dead roaches (they still contribute allergens), keep the bait in place, and check again with sticky traps in two weeks.

How to get rid of cockroaches (the short version)

1. Identify the species. Small tan roaches in the kitchen = German; large ones near drains = American/oriental.
2. Clean and dry. Degrease behind appliances, store food in sealed containers, take trash out nightly, fix leaks.
3. Bait, don't spray. Gel bait placed as small dots in cracks near hiding places beats over-the-counter sprays and foggers, which scatter roaches and repel them from bait.
4. Add an IGR. An insect growth regulator (hydroprene, pyriproxyfen) prevents nymphs from becoming breeding adults.
5. Monitor. Sticky traps show whether numbers are going down.
6. Seal. Caulk gaps around pipes and baseboards, add door sweeps.

The full step-by-step plan is at how to get rid of roaches.

IGR for roaches: what it does and doesn't do

An IGR won't kill the roaches you see today. It makes the next generation sterile or deformed so the colony collapses over several weeks. IGRs are sold as point-source discs, aerosols, or mixed into some gel baits. They are especially useful in apartments where re-infestation from neighbors is constant. Pair an IGR with bait; on its own it is too slow.

What people who dealt with roaches say

Reading through dozens of pest-control forum threads, the same story repeats:

• The first attempt is almost always a spray or a bomb - by the tenant or by building management - and it doesn't stick. Pros on r/pestcontrol consistently say quarterly baseboard sprays and foggers just scatter German roaches; people report "two bombings and still finding adults and babies in the sink."
• Gel bait is what turns it around. Several technicians point out the bait is the attractant - you don't need to lure roaches to it, just put many small dabs where they walk (cabinet hinges, under the sink, behind the stove and fridge). One renter in New York described the typical arc after a pro applied gel: day 7 mostly dying babies, nothing visible by about day 10.
• Seeing only babies after treatment is normal. Egg cases carried by females are protected from bait; the nymphs that hatch later still have to eat it. Keep bait fresh for at least a month.
• Apartments are a building problem. People in multi-unit housing often clear their own unit and get re-infested; techs recommend sealing pipe penetrations, sticky traps by the fridge as an early warning, and pushing management for a building-wide plan rather than paying for one unit.
• Heavy infestations reach places people don't expect: refrigerator motor compartments, electronics, shoes, and stored boxes. These need bait stations next to the appliance and sometimes professional dusting.

When to call a pro

Call a licensed pest control company if you live in a multi-unit building (roaches move between units through plumbing chases), if you still catch nymphs after 6-8 weeks of consistent baiting, if someone in the home has asthma, or if you run a food business. Typical US prices are roughly $150-$400 for an initial German cockroach service with 1-2 follow-ups (approximate, varies by region). See cockroach extermination.