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The chemical cues that pull roaches together can also show you where to put baits and traps.

How Do Roaches Communicate? Droppings, Pheromones, and Touch

Roaches communicate mainly with chemicals in their droppings and on their bodies. What the research shows, and how to use it to place baits and traps.

11 min read

Roaches communicate mostly through chemicals, not sound. The best-studied example is the German cockroach, the most common roach in kitchens and bathrooms. Its droppings give off odors that attract other roaches and encourage them to settle in the same hiding spots. North Carolina State University researchers found that bacteria in the roach's gut help produce many of those odors. Females also release a sex pheromone that draws males. When roaches touch, their antennae pick up waxy compounds on each other's bodies that signal sex and group identity. For a homeowner, the practical lesson is that droppings are a map. UC IPM advises putting baits near hiding spots and next to fecal specks, because those deposits contain a natural attractant.

Most of the detailed research covers the German cockroach and, to a lesser extent, the American cockroach. Other species may behave differently, so treat the findings below as the best-documented examples rather than rules for every roach.

The Short Version: Three Ways Roaches Send Signals

  • Airborne odors. Roaches pick these up from a distance. They include aggregation cues from droppings and the sex pheromones that females release.
  • Contact chemicals. A roach's body is coated in waxy compounds called cuticular hydrocarbons. Other roaches "read" them by touching with their antennae.
  • Touch and sound. Physical contact matters when roaches are clustered together. Sound matters for a few species, like the Madagascar hissing cockroach, but isn't a known part of how common household pests communicate.

Why Roaches Cluster: Signals in Their Droppings

German cockroaches spend most of their time packed into cracks and crevices. UF/IFAS Extension notes they prefer places near food and water. That clustering isn't random. Their droppings, also called frass, act as an "attractant and arrestant": the odor draws roaches in and encourages them to stay.

In a 2015 study in *PNAS*, researchers identified 40 volatile carboxylic acids in German cockroach feces. Roaches raised without gut microbes produced feces lacking 12 of the major compounds, and young roaches strongly preferred feces from normal roaches. As one of the researchers put it in an NC State news release, "When you lose the gut bacteria, you lose the aggregation pheromones."

The same research team found in 2026 that newly hatched roaches eat feces from their colony's shared droppings pile. This helps them develop a preference for their own group's scent. Earlier work by Lihoreau and Rivault showed that German cockroaches can tell siblings from unrelated roaches using body chemicals they sense through antennal contact.

Why does clustering help roaches? The PNAS authors note that contact with other roaches speeds up how quickly nymphs develop. They add that grouping may also help with finding mates, avoiding predators, regulating temperature, and preventing water loss.

What this means for you: a tight, dark gap with dark specks, smears, shed skins, or egg cases around it is likely an active hiding spot. The droppings themselves help keep roaches coming back. Our guide to what the black dots roaches leave behind are can help you recognize those signs, and how to find the roach nest walks through where to look.

Do Roaches Leave Scent Trails?

Partly, but not the way ants do. In a 2000 study, University of Florida researchers found that German cockroaches followed trails of fecal extract more closely than control trails. Adult males followed most accurately, and pregnant females least. The authors pointed out, however, that roaches aren't thought to lay these trails on purpose. Droppings build up along routes roaches travel often, such as between a hiding spot and food, and those routes become scented over time.

The earlier version of this article said roaches use dedicated trail pheromones to lead each other to food. That overstated the evidence. Trail-following from droppings is documented, but deliberately marked trails are not.

Sex Pheromones and Courtship

Roach mating depends on chemistry at two ranges.

At a distance, the female German cockroach releases a volatile sex pheromone called blattellaquinone. It was identified in a 2005 *Science* paper by researchers at Cornell and NC State. According to Cornell's announcement, males follow the odor plume to its source, and the synthetic pheromone proved a highly effective lure in field trapping tests. American cockroach females use a different system: their main attractant, periplanone-B, draws males and triggers courtship. A 2024 study found that a second component, periplanone-A, can dampen that response.

Up close, a mature female German cockroach carries a contact sex pheromone in the waxy layer on her body. A male detects it by touching her with his antennae, then raises his wings in a courtship display. A 2019 study in *Scientific Reports* found that in crowded groups, female pheromone can rub off onto males' antennae and confuse other males. Antennal grooming removes that residue and helps males tell the sexes apart again.

The old version of this article said females attract multiple males in a "dating game" and that some species coordinate care for their young with chemical signals. We didn't find support for either claim about common household roaches in the research we reviewed, so we've removed them.

How Roaches Use Their Antennae

Antennae are a roach's main tool for reading these signals. They carry receptors for smell and taste as well as touch. That's how a male detects a female's contact pheromone and how roaches recognize relatives. Roaches also groom their antennae constantly. The 2019 study found that grooming clears away built-up body wax and keeps the antennae sensitive.

Roaches often seem to vanish before you reach them. UC IPM notes that almost all cockroaches are nocturnal and tend to scatter when disturbed. The previous version of this article said roaches release an "alarm pheromone" to warn each other of danger. We didn't find good evidence for that in common household roaches in the sources we reviewed.

Do Roaches Make Sounds?

The German and American cockroaches that infest homes aren't known to communicate by sound. The well-known exception is the Madagascar hissing cockroach, a large species kept as a pet and classroom insect. It isn't a household pest. It hisses by forcing air through its breathing holes (spiracles), and people can easily hear it. A 2014 paper in *Bioscience Horizons* describes three types of hiss: males hiss during fights and courtship, and all adults produce a louder "disturbance" hiss when handled.

The previous version said roaches communicate by rubbing their legs together to make sounds too high for people to hear. That doesn't describe common household roaches, and the best-known roach sound is quite audible.

Using Roach Communication To Place Baits and Traps

None of this research gives you a secret weapon, but it does point to sensible choices.

  1. Use sticky traps to find the hot spots. UC IPM calls sticky traps the best way to detect and monitor roaches. UF/IFAS recommends placing them along walls, in corners, and close to suspected hiding spots, where roaches travel. Check them daily for several days to see where catches are highest. For how many to use, see how many roach traps you need.
  2. Put bait where the droppings are. UC IPM says to place baits near hiding places or where roaches will find them while foraging. It adds that baits can go next to fecal specks, which contain an aggregation pheromone. Follow the product label for placement and amounts.
  3. Keep sprays and cleaners off bait. Don't spray insecticides or wipe cleaners over bait placements, which can contaminate the bait. Check the product label for any specific directions.
  4. Give baits time to spread. In a 2023 *Journal of Economic Entomology* study, young nymphs that stay near their hiding spots ate feces from adults that had eaten bait, and some died as a result. This "secondary kill" is one way bait reaches roaches that never leave the harborage.
  5. Switch baits if roaches ignore one. Some German cockroach populations have evolved to taste glucose as bitter. In a 2013 *Science* study, NC State researchers found these roaches reject glucose and baits made with it. The 2023 study also found that baits with glucose-containing sugars reduced secondary kill in those populations. If a bait isn't being eaten, a product with a different formulation may work better. Our guide on how to tell if roach bait is working covers what to watch for.
  6. Don't count on pheromone lures alone. Sex and aggregation pheromones have shown promise in research traps. The 2026 NC State team suggested that a species-wide aggregation pheromone could make traps and baits more effective in the future. For now, UC IPM treats sticky traps as a detection and monitoring tool. It also says pesticides alone won't solve a roach problem, and that control usually takes several methods used together.

Should You Clean Up Roach Droppings?

Yes, in most living and food areas. There's a timing tradeoff to plan around, though.

Droppings do more than attract roaches. The EPA says that roach droppings and body parts can trigger asthma, and UC IPM identifies roach infestations as a risk factor for asthma in children. Cleaning up droppings, crumbs, and spills reduces allergens and removes some of the food that competes with bait. UF/IFAS describes removing food, water, and hiding places as key to German cockroach control.

Droppings are also useful signs, and they help attract roaches to bait. A practical approach:

  • Map before you scrub. Note where droppings are heaviest, and set traps or bait there first.
  • Clean food-prep surfaces, dishes, and open living areas promptly, especially if someone in the home has asthma or allergies.
  • Leave active bait placements alone. Clean around them without spraying or wiping the bait itself.
  • Seal and clean hiding spots after the population drops, so leftover droppings don't keep drawing new roaches to the same cracks.

For safe cleanup methods, see how to clean roach droppings. For a full control plan, including when to call a professional, see how to get rid of roaches.

Frequently Asked Questions

Can roaches tell other roaches where food is?

Not directly. German cockroaches follow the scent of droppings, which build up along routes between hiding spots and food. That can lead other roaches toward food, but research doesn't show roaches deliberately marking food for each other.

If I see one roach, does that mean it has signaled others to come?

No. One roach doesn't call in others the way the old version of this article suggested. But German cockroaches live in groups. If you see one, especially in daytime, others are likely hiding nearby, so set sticky traps to see how widespread the problem is.

Do dead roaches attract more roaches?

We didn't find strong research on dead roaches as an attractant. Droppings, which build up wherever roaches live, are the better-documented draw. Remove dead roaches and clean up droppings in living areas, and keep baits in place.

Can I use roach pheromones to lure them out?

Researchers have identified sex and aggregation pheromones that work in trapping tests. Don't assume a store-bought trap contains them unless the label says so. Traps are most useful for showing where roaches are active.

Why do roaches gather in the same spot after I clean?

Cleaning visible droppings doesn't remove residue deep in cracks, and roaches still prefer the same tight, warm spaces. Place bait near those spots, and seal gaps once the infestation is under control.

Do all roach species communicate the same way?

No. Most detailed research covers the German cockroach, with some on the American cockroach. They use different sex pheromones, and some species, like the Madagascar hissing cockroach, also use sound.

Sources

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