Cockroach species differ in their preferred harbourages, breeding rates and movement patterns. Therefore, correct identification helps technicians choose appropriate inspection and treatment methods.
People sometimes confuse German and American cockroaches, but their size, markings and typical locations can help you tell them apart.
Size and Appearance
| Feature | German Cockroach | American Cockroach |
|---|---|---|
| Adult size | Approximately 12–15 mm long | Approximately 35–40 mm long |
| Colour | Amber, light brown or tan | Reddish-brown |
| Markings | Two dark, lengthwise stripes on the section behind the head | A pale yellow border around the upper part of the thorax |
| Wings | Wings extend over the abdomen, but German cockroaches do not appear to fly | Fully winged and capable of flying short distances in warm conditions |
| Body shape | Small and slender | Large and elongated |
The Australian cockroach can resemble the American cockroach. However, Australian cockroaches usually have noticeable yellow markings along the outer edges of their forewings. Size and colour alone may not provide a reliable identification.
Where Each Species Lives
German cockroaches primarily infest indoor environments. They favour warm, humid and undisturbed areas close to food and water.
Common harbourages include:
- Beneath sinks
- Inside cupboards and drawers
- Behind refrigerators and cooking appliances
- Around electrical equipment
- Inside cracks and crevices in kitchens and bathrooms
German cockroaches can also spread to new properties inside cardboard boxes, food packaging, appliances and other transported items.
American cockroaches usually gather in warm, moist and dark areas. They may live indoors or outdoors, depending on the climate and available harbourage.
Common locations include:
- Subfloor, wall and roof voids
- Sewers and drainage areas
- Grease traps
- Rubbish storage areas
- Commercial kitchens, bakeries and food-storage facilities
- Damp service and utility areas
American cockroaches often travel farther from their harbourages while searching for food and water.
Behaviour and Life-Cycle Differences
- German cockroaches reproduce more quickly than American cockroaches and can establish large indoor populations in a relatively short period.
- German cockroaches often gather close to food, warmth and moisture, particularly inside kitchens.
- American cockroaches may move through drainage, sewer and service areas before entering a building.
- German cockroaches have wings but do not appear to fly.
- American cockroaches can fly short distances in warm conditions.
German cockroaches can develop from hatchling to adult in as little as approximately 40 days under favourable conditions. In comparison, American cockroach nymphs may take around 6–12 months to reach adulthood. Temperature, food, moisture and other environmental conditions can affect these timeframes.
Why the Difference Matters for Treatment
Although some control methods overlap, technicians must target the areas where each species lives and travels.
German cockroach control commonly focuses on:
- Kitchens and food-preparation areas
- Cracks and crevices near heat, food and moisture
- Cupboards, drawers and appliance areas
- Targeted gel baits, dusts or registered insecticides
- Sanitation and removal of competing food sources
- Follow-up inspection and monitoring
The technician must apply every pesticide according to its registered label. Poor hygiene can also reduce the effectiveness of chemical control.
American cockroach control commonly focuses on:
- Sewers, drains and grease traps
- Subfloor, wall and roof voids
- Rubbish and waste-storage areas
- Plumbing and service entry points
- Moisture, leaks and drainage problems
- Exterior harbourages and potential entry points
The treatment plan may include targeted baits, dusts or residual treatments where the product label permits their use. Exclusion, cleaning and moisture management may also form part of the plan.
Using a treatment intended for the wrong harbourages may produce poor results. For example, treating only kitchen cabinetry may miss an American cockroach population associated with a subfloor, drain or grease trap.
Not Sure Which One You Have?
A small, amber cockroach with two dark stripes behind its head may be a German cockroach. A much larger, reddish-brown cockroach with a pale border behind its head may be an American cockroach.
However, Australia has several pest cockroach species with overlapping colours, sizes and habitats. These include Australian, smokybrown, Oriental and brownbanded cockroaches. Therefore, avoid identifying the species from location or colour alone.
Not sure which species you have? Contact Newcastle Pest Exterminators for professional identification and a treatment plan based on the species, harbourage areas and level of activity.
