Cockroach

Structure, Appearance and Characteristics

Adults:

• Approx. 30-35mm in length.
• Yellow border on pronotum (area behind the head) is very distinct.
• Dark Reddish brown in colour.
• Light markings on thorax.
• Yellow streaks on the sides at the base of the wing covers (elytra).
• Wings completely cover abdomen.
• Chewing mouthparts.
• Nocturnal.
• Will fly in warm weather.

Nymph (The Young):

• Look similar to adult but wingless.
• Brown in colour until later instars (moults) which become more like the adult colouring.
• Later instars posses distinct bright yellow spots along the margins of their abdomen.

Life Cycle

Gradual / Incomplete metamorphosis (egg – nymph – adult). Eggs are encased in an egg capsule (Ootheca). Female drops the egg capsule (Ootheca) shortly after it is formed near a food source, in crevices, on walls, or under workable material such as moist wood, so as to camouflage it. Eggs per capsule: 16-24. Incubation period: 30-40 days. Nymphal period: 6-12 months Nymphs normally moult 10-12 times to reach adulthood. Females may produce 12-30 egg capsules in a lifetime. Egg capsules are completed and dropped at about 10 day intervals. Adult lifespan: up to 8 months.

Habitat

Found mostly outdoors. Often found under bark of trees, woodpiles and locations with moist and decaying vegetable matter. Can be found inside homes in cupboards, behind drawers, in all food areas and industrial areas, subfloor areas, wall and roof voids. Favours warm, humid environments. Is not found as readily in cooler climates compared to the American cockroach (Periplaneta americana).

Food

Omnivorous. Scavenger. Prefers decaying organic vegetable matter. Will feed on starch materials such as book bindings.

Economic Impact / Nuisance

Presence can cause anxiety or stress. Secretions can affect some humans (e.g. allergic reactions such as asthma). Dense populations can leave a distinct odour. Food and utensils can be contaminated with droppings, cast skins, empty egg cases and vomit marks. A number of pathogenic organisms have been associated with cockroaches. Their ability to act as vectors of pathogens is still a matter of controversy. This is mainly because that transmission can only occur indirectly via contamination of food and utensils. Pest status applies equally to nymphs and adults.

Control

Cockroaches have aggregation characteristics which builds a more suitable environment to inhabit. They favour cracks and crevices for harbourages where they can contact the top and bottom surfaces with their body. They do not leave their harbourages except for food, water and mating. Their aggregation characteristic can be used against them, since finding a harbourage will yield more than one individual. Pheromones are not volatile, so contact with other individuals in the population is necessary, which can help spread insecticide to some degree.

Control should be targetted at their harbourages since they stay in these areas for large amounts of time. Physical exclusion (e.g. caulking up cracks) is useful since the cockroach population is proportional to the number of harbourages available. Chemical treatments into cracks and crevices is also valuable since prolonged contact with treated surfaces will yield a high mortality rate. Applying proper hygiene measures can also be useful, forcing the cockroaches to travel further to find food and water, which increases the chances of contacting treated surfaces outside harbourage areas.