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Blattodea (cockroaches, roaches; phylum Arthropoda, class Insecta) Order of medium to large, exopterygote insects in which the fore wings are modified as rather strongly sclerotized tegmina. Wings are absent in some groups. The legs are gressorial, and the body is dorsoventrally compressed. Auditory organs are absent. Females have a small, concealed ovipositor, and eggs are laid in an ootheca. Most cockroaches are nocturnal, and during the day are usually found hiding in crevices. Burrowing and cave-dwelling species are known, and some species are even amphibious. Cockroaches may be adapted to desert conditions, or live in tropical rain forest. It is thought that most cockroaches are omnivorous. Of the approximately 3500 species known, some are of economic importance as domestic pests.