Cockroaches are large dark beetles. The natural habitat of the cockroach is warm, moist conditions found in tropical and subtropical countries. However, they have found similar conditions in the kitchens, bath-rooms, ducts and sewers of more temperate regions. This combination of habitats makes these insects a particular health hazard. They will crawl from dustbin or sewer onto kitchen work surfaces, perhaps carrying disease organisms on their feet and mouths. Their life cycle includes a stage in which the eggs are encased in a hard chitinous case, which can lie dormant for several months and is largely protected from insecticide. Three species are commonly encountered in New Zealand, the Oriental Cockroach (Blatta orientalis), American Cockroach (Perplaneta Americana) and the German Cockroach (Blattella germanica).
Cockroaches are nocturnal (active at night) and conceal themselves during the day in cracks and crevices, often around drains, sinks, cookers and in ducting. The mated female will lay (Oriental) or carry (German) the chitinous “purses” containing eggs or nymphs. When the eggs hatch the nymphs look like adult cockroaches in miniature but have to go through several molts before becoming sexually mature. Cockroaches are gregarious, and given favourable conditions can produce very large infestations of hundreds or thousands of individuals. In large numbers the infestation will produce a distinctive offensive odour.
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