Australian cockroach (Periplaneta australasiae) is a large species of cockroach in the family Blattidae. Despite its common name, it is not thought to be native to Australia and is widely distributed in warm, humid regions around the world. It is most often an outdoor pest that may enter buildings in search of moisture, food, or shelter, especially during hot weather or heavy rains.
Taxonomy and classification
- Kingdom: Animalia
- Phylum: Arthropoda
- Class: Insecta
- Order: Blattodea
- Family: Blattidae
- Genus: Periplaneta
- Species: P. australasiae
Description
Adult Australian cockroaches typically measure 30–35 mm (1.2–1.4 in) in length and are reddish-brown to dark brown. They are often identified by yellow markings along the outer edge of the pronotum (the shield-like plate behind the head) and yellow streaks near the base of the wings. Both sexes have fully developed wings that may extend past the abdomen, and adults can fly short distances in warm conditions.
Nymphs (immature cockroaches) resemble adults in shape but are smaller, darker, and wingless. As nymphs grow, they molt multiple times before becoming adults.
Distribution and habitat
The Australian cockroach is considered cosmopolitan in distribution, especially across tropical and subtropical climates. It is established in many regions including Australia, parts of the southeastern United States, Central and South America, Africa, Southeast Asia, and various Pacific islands.
This species prefers warm, moist environments and is commonly found outdoors in mulch, leaf litter, gardens, greenhouses, compost, woodpiles, and around building foundations. Indoors, it may be found in basements, crawl spaces, boiler rooms, attics, or any area with elevated humidity and access to water.
Behavior and ecology
Australian cockroaches are primarily nocturnal, hiding during the day and emerging at night to forage. They are omnivorous scavengers and will feed on a wide range of materials, including decaying plant matter, food scraps, grease, paper products, and other organic debris.
Outdoors, they may contribute to the breakdown of organic material. Indoors, they are unwanted due to contamination risks and their ability to spread allergens.
Life cycle and reproduction
The Australian cockroach develops through three stages: egg, nymph, and adult. Females produce egg cases called oothecae, each typically containing about 20–24 eggs. Oothecae are deposited in protected, humid places where they are less likely to dry out.
Nymphs hatch from the ootheca and grow through a series of molts. Depending on temperature, humidity, and food availability, the life cycle may take 6–12 months to complete.
Interaction with humans
Pest status
The Australian cockroach is considered a nuisance and occasional structural pest. It is often more common outdoors than indoors, but it can enter homes and businesses through gaps around doors, windows, vents, and utility penetrations. Indoor activity may increase when outdoor conditions become unfavorable.
Like other cockroaches, it can contaminate food and surfaces and may contribute to asthma and allergy symptoms in sensitive individuals due to shed skins, droppings, and allergenic proteins.
Damage
Australian cockroaches may damage paper products, cardboard, book bindings, and certain fabrics. In gardens and greenhouses, they may also feed on tender plants and seedlings, particularly when other food sources are limited.
Control and management
Management typically relies on integrated pest management (IPM), focusing on moisture control, sanitation, and exclusion. Because this species often originates outdoors, reducing exterior harborage is especially important.
- Reduce moisture: fix leaks, improve ventilation, and use dehumidifiers in damp areas.
- Exclude entry points: seal cracks, install door sweeps, screen vents, and seal utility penetrations.
- Remove harborage: keep mulch and leaf litter away from foundations; reduce clutter and organic debris.
- Sanitation: store food in sealed containers and clean crumbs, grease, and spills promptly.
- Baits and IGRs: use gel baits and insect growth regulators in high-activity areas as needed.
- Targeted insecticides: apply residual treatments to exterior entry points and harborage zones when infestations persist.
Similar species
The Australian cockroach is commonly confused with the American cockroach (Periplaneta americana). A frequent distinguishing feature is the yellow edging and streaking on the pronotum and near the wings of the Australian cockroach, which is less pronounced or absent in the American cockroach.