Cockroaches

• 10 – 16 mm in length

The colour can vary greatly from a tan colour to a dark brown.

This species has two dark lines running from the back of its head (pronotum) to the base of their wings.

Although this cockroach has wings, it can barely fly and rarely does so.

Found commonly around human populations, the German cockroach prefers warm, humid, and dark environments.

They can be found anywhere in the home but are commonly found in and around kitchen and bathroom areas such as under refrigerators and dishwashers, inside cupboards, drawers and electrical appliances. Other areas might include drains, ducts and other underground structures.

The German Cockroach is the most sociable of the pest species and is often found in large groups, especially near warm areas like water heaters.

Although nocturnal, the German cockroach is occasionally seen during day, especially if the population is crowded or has been disturbed. However, sightings are most frequent of an evening, when someone suddenly brings a light into a room deserted after dark, such as a kitchen where they have been scavenging.

When excited or frightened, the species emits an unpleasant odour.

Although they only live for up to six months, the German cockroach is probably the most troublesome of all cockroach species.

This is due to a number of reasons, such as:

– Sexual maturity attained within several weeks.

– Prolific reproduction: One female German cockroach can produce up to 20,000 young annually. Unlike other species of cockroaches that drop their oothecae (egg case), German cockroach females carry their ootheca until they are ready to hatch which protects them from predation. This case carries on average 30-40 eggs in it.

For effective control measures to be achieved, they must be systematic, comprehensive and sustained. Pest populations can be recreated within a few generations with the survival of just a few eggs. Re-colonisation from surrounding areas can also be very rapid.

• 30 – 50 mm in length

The American cockroach is the largest of the pest species.

The American cockroach is a reddish brown colour with a pale-brown or yellow band around the edge of the pronotum (shield like structure over the head). Although very similar to the Australian cockroach, the yellow markings on the American cockroachs’ pronotum are not well defined and also do not have the yellow markings on their wings.

Once the American cockroach has reached adulthood, wings develop allowing the roaches to fly for very short distances.

American cockroaches generally live in warm, moist areas, but can survive in dry areas if they have access to water. They prefer high temperatures around 29 °C however, in cooler regions they tend to be found indoors as they do not tolerate low temperatures.

They commonly infest hospitals, bakeries, food stores, warehouses, factories and domestic residences. The American cockroach is an omnivorous and opportunistic feeder so can be found almost anywhere as they scavenge for food.

These cockroaches tend not to infest homes the way that German cockroaches do, partly due to their larger size. Nonetheless, these cockroaches are common in wall and roof voids, crawl spaces, cracks and crevices of porches, foundations, drains and sewers.

It seems to prefer decaying organic material, but will eat most human or animal foods as well as paper and clothing. They have also been observed to feed upon dead or wounded cockroaches of their own or other species.

The American cockroach can travel quickly, often scurrying out of sight when a threat is perceived, and can fit into small cracks and under doors despite its fairly large size. It is considered one of the fastest running insects.

Cockroaches produce a chemical called an “aggregation pheromone” causing the roaches to stay together in groups. The odour of these pheromones is sometimes described as having a “musty” smell. People with sensitive noses may begin to notice this odour as the roach population starts to grow.

The American cockroach is second only to the German cockroach in abundance.

Females produce an egg case (ootheca) which protrudes from the tip of the abdomen. On average, females produce 9–10 oothecae, or roughly one egg case a month for ten months.

Each egg case is about 0.9 cm long and contains 16 eggs.

After about two days, the initially brown capsule-shaped egg cases are placed on a surface in a safe location, close to a food source and then turn black in colour.

Immature cockroaches emerge from egg cases in 6–8 weeks . After hatching, the nymphs feed and undergo a series of 13 moultings (or ecdysis) and require 6–12 months to mature.

Adult cockroaches can live up to two years, during which females produce an average of 150 young. The American cockroach reproductive cycle can last up to 600 days.

An adult without food or a water source may survive for about two to three months.

With a length of 23–35 mm it is very similar in appearance to the American cockroach and may be easily mistaken for it.

It is, however, slightly smaller than the American cockroach, and has a yellow margin on the thorax and yellow streaks at its sides near the wing base. These markings are clearly defined on the pronotum (shield like structure over the head) and on the foremargins of the forewing.

Like most other cockroaches, the Australian cockroach is a scavenger. The Australian cockroach however, prefers food of plant origin so is most commonly found outdoors.

Often under bark of trees, in leaf litter in gardens, among wood piles, in greenhouses, outhouses, and in other locations that offer moist, decaying vegetable matter. They can also be found in subfloors, wall voids, roof voids, garages and sheds.

It prefers warmer climates and is not cold-tolerant but it may be able to survive indoors in colder climates.

It does well in moist conditions, but also can tolerate dry conditions as long as water is available.

Australian Cockroaches tend to be more frequently encountered in warm, subtropical and tropical conditions and they are known to fly in warm weather.

They are often seen darting out of sight when someone enters a room and can fit into small cracks and under doors despite its fairly large size. It is known to be very mobile and able to fly short distances.

Females deposit the ootheca (egg case) containing 24 eggs a day after production.

After hatching nymphs take 6-12 months to develop into adults.

Relatively small in size.

• Adult male (14 mm)
• Adult female (10 mm)

The female brown-banded cockroach (pictured) has a noticeably larger abdomen than the male.

Brown-banded cockroaches are pale brown with two light bands of yellow or cream across the thorax and abdomen. The bands are quite noticeable on nymphs and females.

Males have wings covering the full length of the abdomen, however the wings of females are shorter than the abdomen. The males fly when disturbed whereas the females are unable to.

The brown-banded cockroach resembles the German cockroach (Blattella germanica) with its small size and body shape but it can be distinguished by the absence of two dark pronotal stripes.

The brown-banded cockroach is primarily an indoor pest. Unlike German cockroaches that are mainly found near warm, moist areas, the brown-banded cockroach prefers a less humid environment and tends to distribute throughout homes.

They are commonly found in furniture, behind pictures or in lounge suites. It is for this reason that they are sometimes referred as the “furniture” cockroach.

The brown-banded roach is mostly active at night in search of food and is an opportunistic feeder. Sightings of brown-banded cockroaches during the day are not unusual and due to their dispersal throughout all areas of a building they can be difficult to control if the technician is not highly trained.

This cockroach prefers food sources with high starch content and will attack wall paper and book bindings.

They are known to frequently fly when disturbed or when temperatures are high.

Females produce a relatively small (5mm) yellow to reddish-brown ootheca (egg case) which contains up to 18 eggs. Each adult female can to produce about 13 oothecae in her lifetime.

The egg case is usually carried by the female for 24 to 36 hours before being attached to a surface, usually on the upper third of walls. Oothecae are commonly found in clusters when population density is high.

Development from nymph to adult takes about 2 to 4 months and they can live for  approximately 3-6 months depending on conditions. Each female will produce between 100-260 offspring.