Cockroaches have changed little during the 400 million years they have been around. Most species are of tropical or subtropical origin. Although they are not social insects, they are gregarious or commonly occur in groups. They will feed on practically anything of nutritive value.
Cockroaches are among the most important pests of households and commercial establishments. Not only is their mere presence a nuisance but they are known to be capable of carrying many common disease pathogens as well as causing allergic reactions in many people.
Oval in outline, body usually flattened, head partially or entirely concealed beneath pronotal shield (expanded pronotum). Front wings leathery with veins, although veins may be reduced. Antennae long and threadlike. Abdominal cerci usually long, not forceps-like. Tarsi 5-segmented. Mouth parts chewing.
It is advisable to know the cockroach species being encountered because cockroaches vary in their food preferences and living habits. PMANZ Technicians are trained in insect identification and we will provide a free inspection.  
Cockroaches have simple metamorphosis: egg, nymph, adult. Nymphs and adults are usually similar in appearance except for size and the typical addition of wings in the adult of most species; all newly emerged cockroaches are white, but will assume their typical coloration within a few hours as their cuticle hardens. They are gregarious, thus all stages and instars are found together in their preferred harborages, except that they tend to be size segregated by crack/crevice thickness.
Domestic species are nocturnal or active at night but will be found out during daylight when the infestation is very large and acceptable harborages are filled to overflowing with cockroaches.

Know Your Enemy - A complete Cockroach Guide

For more information on cockroaches and your health follow this link :

Control: ( Cockroach control is a 5-step process.) 
  1. Prevention. 
  2. Good Sanitation 
  3. Inspection. 
  4. Initial insecticide application. 
  5. Follow-up or maintenance service.