Although 4,650 different species of cockroaches are presently cataloged and scientifically accepted worldwide, there are astonishingly at least twice to four times that many still to be discovered. In other words, everything we presently know about the species represents, at best, only one-third of this insect group's total make-up.

A Secretive Clan 

Another often-overlooked fact about cockroaches is that there are just two dozen or so species that like to openly congregate in areas frequented by humankind. As such, this tiny fraction of the group is the exception rather than the rule; the great majority of cockroach species - 99.5% - are more secretive insects burrowing far from the human eye. This is a good thing, as among them is the largest of all cockroach species, the Australian rhinoceros cockroach, which can weigh up to 1.2 ounces and grow to a length of 3.1 inches. By contrast, the smallest species, the Attaphila fungicola, clocks in at less than one-tenth of an inch and likes to live in the nests of leaf cutter ants.

Five Major Families 

Cockroach species are divided into five major Latin named families: Blaberidae, Blatellidae, Blattidae, Cryptocercidae and Polyphagidae. Among the first group is the German cockroach, one of the most pervasive human pest strain of the species.  Females carry their eggs with them until they hatch, making it more difficult to combat the propagation of this species. Other factors that have led this particular species to become such a household scourge include the fact that it lays more eggs than most other cockroaches, and does so more often each year (three to four times).

Although the name German cockroach might suggest that it originated in Germany, it is thought to actually be originally indigenous to southeast Asia, having later entered Europe during the time of Marco Polo, carried along trade routes by traveling merchants. Strangely, in Germany, it is sometimes called the Russian roach, while in Russia it is referred to as the Polish roach.

The largest species of cockroach found in human dwellings is the American cockroach, again belying its name as it is thought to have North African origins. This species can grow to a length of up to an inch and a half, with males sometimes living as long as 15 months. Both sexes have wings and can fly. Two of the other species of cockroach found in human dwellings are the Brownbanded and Oriental varieties. Overall, cockroaches span a remarkable range of sizes, shapes, colors and behavior. Their range of habitats is equally diverse, encompassing caves, mountains, deserts, forests and, of course, kitchens.