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What Eats Roaches? The Real Predators, and Why They Won't Fix Your Infestation

Parasitoid wasps, geckos, centipedes, spiders and birds all eat cockroaches. What the research shows, and why none of it works as home pest control.

11 min read

Plenty of animals eat cockroaches, and the catalogue is remarkably well documented. Roth and Willis's Smithsonian monograph *The Biotic Associations of Cockroaches* compiled records of roughly 4 species of fish, 16 amphibians, 12 reptiles, 20 birds, and 27 mammals that prey on cockroaches, plus about 4 centipedes, 4 spiders, 2 scorpions, and 90 insects — including a set of parasitoid wasps that lay eggs inside cockroach egg cases. But the serious biological control work on those wasps, reviewed in WHO's *Public Health Significance of Urban Pests*, has produced mixed and mostly narrow results, and Auburn University's extension entomologists conclude in their cockroach biocontrol review that biocontrol alone is unlikely to exterminate an infestation and is best suited to outdoor pest management. No predator you can buy, keep, or attract will clear cockroaches from a house. Do not introduce an animal to your home as pest control.

The Parasitoid Wasps That Actually Work On Cockroaches

This is the most interesting part of the field, and the only part where controlled results exist. These wasps do not hunt adult cockroaches; they attack the ootheca, the hardened egg case, and their larvae eat the eggs inside.

Aprostocetus hagenowii

A tiny eulophid wasp, 1.3 to 2.1 mm long, that parasitizes the oothecae of large peridomestic cockroaches — American, Oriental, Australian, brown, and smokybrown. Development takes 32 to 46 days, and WHO's review notes that roughly 30 to 93 adult wasps emerge from a single parasitized egg case.

Two findings matter for anyone hoping to use it:

  • It does not work on German cockroaches. A 2025 host-range study in the Journal of Insect Science by Smith, Fadamiro and Appel, Host range of the oothecal parasitoid *Aprostocetus hagenowii*, found no successful parasitism of Blattella germanica oothecae, and states that the consensus is that older reports listing it as a host are erroneous. Since German cockroaches drive the overwhelming majority of indoor infestations, that alone rules the wasp out for most households.
  • Field releases have underperformed. WHO's chapter reports that releases of this wasp in sewers did not become established and did not control American cockroaches.

Where it does show up, it is a genuine natural enemy. In a Virginia field study cited by WHO, about 51% of oothecae recovered from outdoor sites were parasitized — 36% by A. hagenowii and 15% by an ensign wasp.

Ensign wasps (Evania appendigaster and Prosevania punctata)

These are the black, wasp-shaped insects with a small flag-like abdomen that people sometimes find indoors and assume are a problem. They are not. They lay eggs in cockroach oothecae, and their larvae destroy the eggs.

Two practical limits: in the same Virginia study, none of the oothecae placed inside the structure were parasitized even though adult ensign wasps were regularly collected indoors, and Thoms and Robinson found that 60% of homeowners killed the wasp on encountering it. If you see one, leaving it alone is the right call, but it is not a control program.

Comperia merceti

The best-studied indoor biological control of a cockroach, and worth understanding because it shows what success actually looks like. This encyrtid wasp attacks brown-banded cockroach oothecae only. In an insect rearing facility, Coler, Van Driesche and Elkinton achieved 70% to 90% parasitism of oothecae after boosting cockroach density, and in follow-up work Hechmer and Van Driesche reported that two parasitoid populations sustained themselves on separate indoor brown-banded cockroach populations for ten years without supplemental releases, with parasitism between 36% and 93%.

That is a real result — in a research facility, against one uncommon species, over a decade. It is not a product you can buy for your kitchen.

Ampulex compressa, the emerald jewel wasp

The one everyone has seen a video of. The female stings a cockroach twice, the second sting delivering venom directly into the brain, which suppresses the escape reflex; she then cuts the antennae and walks the compliant cockroach to a burrow, where her larva consumes it. The life history is documented in Arvidson et al., *Journal of Hymenoptera Research* (2018).

As pest control it has been tried and it failed. Penn State's Frost Entomological Museum notes the species was deliberately introduced to Hawaii in 1941 for cockroach control and the effort is regarded as unsuccessful. WHO's review adds the mundane reasons: these wasps are difficult to rear, and their size makes them unacceptable to people in indoor settings.

The Everyday Predators In And Around Homes

None of these are management tools, but they are the honest answer to the question.

  • House centipedes. Roth and Willis record Scutigera coleoptrata preying on cockroaches on good circumstantial evidence, and in their own experiments a single house centipede caught an American cockroach nymph and then grabbed two more with its legs while still eating the first. They also fed on German and brown-banded cockroaches. They are the most genuinely useful cockroach predator likely to already be in your basement.
  • Geckos and skinks. On Arno Atoll, geckos and night-feeding skinks were recorded eating large numbers of cockroaches, and Beebe kept geckos in a bungalow specifically to help control Periplaneta. This is where the "get a gecko" advice originates. It is also a century old and describes the tropics.
  • Spiders and scorpions. A handful of species are documented cockroach predators. Their effect on a population is negligible.
  • Birds. Beebe recorded cockroaches eaten by 27 species of birds in British Guiana, and poultry eat them opportunistically wherever the two overlap.
  • Amphibians. Toads and tree frogs were historically kept in houses for cockroaches — in Cuba against American cockroaches, and on Australian sugar plantations, where tree frogs were encouraged indoors as pets that hunted large cockroaches.
  • Mammals. Hedgehogs were kept in English kitchens to destroy cockroaches, and mongooses in Hawaii ate large numbers of American and Australian cockroaches.
  • Other cockroaches. Intraspecies predation is routine. Roth and Willis document German cockroaches eating newly molted nymphs and hatchlings, American cockroach females eating their own oothecae and killing males, and starving adults eating eggs and then each other. Cockroaches are their own most consistent predator, and it still does not stop a population from growing.

Nematodes And Fungi: The Closest Thing To A Real Product

Auburn's extension review lists two categories beyond insects: entomopathogenic nematodes such as Steinernema carpocapsae, and fungi such as Beauveria bassiana and Metarhizium anisopliae.

The catch is moisture. WHO cites work finding that the time needed to kill half of exposed cockroaches with S. carpocapsae was inversely related to how moist their preferred habitat was. German and brown-banded cockroaches were the most susceptible species, but they also live in the driest indoor harborages, so delivering viable nematodes where those cockroaches actually are is the unsolved problem. Fungal products face desiccation, spore viability, and bait-station avoidance issues.

Auburn is direct about the limitations: biocontrol is slow, vulnerable to environmental conditions, should not be used in places like restaurants where it may contaminate food, and requires care indoors around pets, since the fungi can infect reptiles. Their bottom line is that it performs best as one component of an integrated program, outdoors.

Why You Should Not Introduce Animals As Pest Control

This is the part the "natural solutions" genre skips.

  1. The math does not work. German cockroaches produce a generation in roughly 100 days and live in crevices a predator cannot enter. Nothing you introduce will out-reproduce them or reach their harborage.
  2. You are adding a second pest. A gecko, frog, or hedgehog in a house needs food, water, heat, and containment. When it dies or escapes, you have a decomposing animal in a wall or an escaped exotic in your neighborhood.
  3. Released non-native animals become invasive problems. Every major house-infesting cockroach in North America is itself an invasive species that arrived by human transport. Repeating the mistake with a predator is not an improvement.
  4. Reptiles and amphibians carry their own health considerations, including Salmonella, which is a specific concern in households with young children.
  5. Predators and insecticides do not mix. If you are baiting, an animal eating poisoned cockroaches is taking a secondary dose you did not plan. If you keep the predator safe by not baiting, you have given up the thing that works. If pets are your concern, choosing a pet-safe roach killer is a better path than adding an animal.

Leaving existing predators alone — house centipedes, spiders, the ensign wasp that wandered in — is reasonable and free. Importing new ones is not.

What Actually Reduces A Cockroach Population

The evidence-backed approach is unglamorous and it works.

  1. Identify the species with sticky monitors at floor-wall junctions, under sinks, and behind appliances. Trap counts are also how you will know whether anything you do is working.
  2. Bait, in many small placements. Gel and station baits are the primary tool. Texas A&M's guidance is many pea-sized placements near harborage rather than a few large ones, and at least one station within one to two feet of every suspected harborage. How long roach bait takes to work sets realistic expectations.
  3. Do not spray near baits. Cockroaches avoid contaminated bait, which cancels the most effective tool you have.
  4. Remove water first, food second. Fix leaks, dry sinks at night, empty pet bowls.
  5. Reduce harborage. Cardboard, clutter, and open cracks in cabinets are habitat.
  6. Treat outdoors separately if you have American, Oriental, or smokybrown cockroaches, since the population lives in mulch, woodpiles, and meter boxes. Keeping roaches out of your yard covers that side.
  7. Switch bait active ingredients if counts have not fallen in two to three weeks, and rotate over time to limit resistance.

The full sequence is in how to get rid of roaches.

Claims From The Previous Version We Could Not Support

The earlier draft of this article recommended several things we found no evidence for, so they are gone:

  • Praying mantises as cockroach control. They are generalist predators, not selective, and there is no body of work supporting them as a cockroach management tool.
  • Hedgehogs and mice as practical predators. Both appear in Roth and Willis as historical curiosities, not recommendations. Mice are a pest in their own right.
  • Bay leaves, cucumber slices, and essential-oil sprays as deterrents. These are folk remedies. See how to use bay leaves for roaches and what plants keep roaches away for what the lab data actually shows about repellency and how briefly it lasts.
  • Boric acid "sprinkled" in activity areas. Boric acid is a legitimate tool but Texas A&M is specific: apply it lightly into voids and crevices so residues are barely visible, never in the open or on counters and shelves where it can contaminate food-contact surfaces. Cockroaches avoid heavy deposits, so over-applying makes it less effective, not more.

Frequently Asked Questions

Will getting a gecko get rid of my roaches?

No. The historical records come from tropical settings and describe modest predation, not control. In a house you would be adding an animal with its own care requirements, salmonella considerations, and incompatibility with the baits that actually work.

Do cats and dogs eat cockroaches?

Some do opportunistically. It is not control, and there is a real conflict with insecticide use, since a pet eating cockroaches that fed on bait is getting a secondary dose. Keep bait in child-resistant stations and out of pet access.

Can I buy parasitoid wasps for cockroaches?

Not as a practical consumer product. The species with the strongest track record, Comperia merceti, attacks only brown-banded cockroaches, and Aprostocetus hagenowii does not attack German cockroach egg cases at all.

Are house centipedes worth keeping around?

They are legitimate predators of cockroach nymphs and adults, and they are harmless to people. Whether you tolerate them is a personal call, but killing them gains you nothing.

Do cockroaches eat each other?

Yes, routinely. They consume their own egg cases, newly molted nymphs, hatchlings, and each other when food runs short. It is one reason populations can persist on very little.

Is there any natural predator that works indoors?

Only in narrow, well-managed research settings, and only against brown-banded cockroaches. For German cockroaches — the species in most infested homes — there is no working natural-enemy option.

Sources

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