File:Cockroach (Blattodea) Laying an Egg.jpg

Could not resist putting this picture I took some days back. It was carrying an egg capsule (ootheca) into which some dozens of eggs are cemented in a double row down the middle.

Cockroaches are generally omnivores. On category of exception exception to this rule is the wood-eating genus Cryptocercus; species occur in Russia, China, Korea and the United States. Although they are incapable of digesting the cellulose themselves, they have a symbiotic relationship with a protozoan that lives in the gut and digests the cellulose, allowing the insect to extract the nutrients. In this, they are similar to termites and current research suggests that the genus Cryptocercus is more closely related to termites than it is to other cockroaches. Cockroaches are most common in tropical and subtropical climates. Some species are in close association with human dwellings and widely found around garbage or in the kitchen.

Cockroaches, like most insects, breathe through a system of tubes called tracheae, a word similar to the name of the tube leading to the lungs in mammals. The tracheae of insects are attached to the spiracles which are small, sometimes valved, openings on each side of most of the body segments, excluding the head. Thus the cockroach can breathe without its head. The valves open when the CO2 level in the insect rises to an unacceptable level; then the CO2 diffuses out of the tracheae to the outside and fresh oxygen diffuses in. The tracheal system brings the air directly to cells because they branch continually like a tree until their finest divisions tracheoles are associated with each cell allowing gaseous oxygen to dissolve in the cytoplasm lying across the fine cuticle lining of the tracheole. CO2 diffuses out of the cell into the tracheole.

Most insects do not have muscular lungs and thus do not actively breathe in the vertebrate lung manner. However, in some very large insects the diffusion process may not be sufficient to provide oxygen at the necessary rate and body musculature may contract rhythmically to forcibly move air out and in the spiracles and one can actually call this breathing. This might be associated with such activities as the energetic flight of the migratory locust. [2]