Anaplectidae Blaberidae Blattidae Corydiidae Cryptocercidae Ectobiidae Lamproblattidae Nocticolidae Tryonicidae Cockroaches (or roaches[2][3][4]) are insects belonging to the order Blattodea (Blattaria).

Modern cockroaches are an ancient group that first appeared during the Late Jurassic, with their ancestors, known as "roachoids", likely originating during the Carboniferous period around 320 million years ago.

They are popularly depicted as large, dirty pests, although the majority of species are small and inoffensive and live in a wide range of habitats around the world.

[12][13][14] Fossil roachoids are considered the common ancestor of both mantises and modern cockroaches, and are distinguished from the latter by the presence of a long external ovipositor.

As the body, hind wings and mouthparts are not preserved in fossils frequently, the relationship of these roachoids and modern cockroaches remains disputed.

The earliest definitive fossils of modern crown group cockroaches, specifically Corydiidae, are known from the Late Jurassic rocks of Russia.

This hypothesis was originally based on similarity of the symbiotic gut flagellates in termites regarded as living fossils and wood-eating cockroaches.

[24] At the other end of the size scale, Attaphila cockroaches that live with leaf-cutter ants include some of the world's smallest species, growing to about 3.5 mm in length.

[26] The spines on the legs were earlier considered to be sensory, but observations of the insect's gait on sand and wire meshes have demonstrated that they help in locomotion on difficult terrain.

Many live in leaf litter, among the stems of matted vegetation, in rotting wood, in holes in stumps, in cavities under bark, under log piles and among debris.

Most of these respire by piercing the water surface with the tip of the abdomen which acts as a snorkel, but some carry a bubble of air under their thoracic shield when they submerge.

In 2005, the role of one of these proteins, pigment dispersing factor (PDF), was isolated and found to be a key mediator in the circadian rhythms of the cockroach.

When a sufficient number of individuals (a "quorum") exploits a food source, this signals to newcomer cockroaches that they should stay there longer rather than leave for elsewhere.

In one study, isolated cockroaches were less likely to leave their shelters and explore, spent less time eating, interacted less with conspecifics when exposed to them, and, among males, took longer to recognize receptive females.

The tracheal system branches repeatedly, the finest tracheoles bringing air directly to each cell, allowing gaseous exchange to take place.

[60] While cockroaches do not have lungs as do vertebrates, and can continue to respire if their heads are removed, in some very large species, the body musculature may contract rhythmically to forcibly move air in and out of the spiracles; this may be considered a form of breathing.

Some species are capable of remaining active for a month without food and are able to survive on limited resources, such as the glue from the back of postage stamps.

Japanese cockroach (Periplaneta japonica) nymphs, which hibernate in cold winters, have survived twelve hours at −5 to −8 °C (23 to 18 °F) in laboratory experiments.

While cockroaches do, indeed, have a much higher radiation resistance than vertebrates, with a lethal dose perhaps six to 15 times that for humans, they are not exceptionally radiation-resistant compared to other insects, such as the fruit fly.

[60] Because of their ease of rearing and resilience, cockroaches have been used as insect models in the laboratory, particularly in the fields of neurobiology, reproductive physiology and social behavior.

It can be used in experiments on topics such as learning, sexual pheromones, spatial orientation, aggression, activity rhythms and the biological clock, and behavioral ecology.

[97] A study conducted by scientists at Purdue University concluded that the most common cockroaches in the US, Australia and Europe were able to develop a "cross resistance" to multiple types of pesticide.

[98] The scientists suggested that cockroaches will no longer be easily controlled using a diverse spectrum of chemical pesticides and that a mix of other means, such as traps and better sanitation, will need to be employed.

[98] Researchers from Heriot-Watt University demonstrated that a power laser can, with high effectiveness, neutralise cockroaches in a home, and suggest it might be an alternative to pesticides.

Running a farm involves relatively low starting and operating costs due to how hardy and easy to process the insects are.

It is mentioned by Aristotle, saying that it sheds its skin; it is described as foul-smelling in Aristophanes' play Peace; Euenus called it a pest of book collections, being "page-eating, destructive, black-bodied" in his Analect.

Pliny the Elder recorded the use of "Blatta" in various medicines; he describes the insect as disgusting, and as seeking out dark corners to avoid the light.

A cockroach given the name Nadezhda was sent into space by Russian scientists as part of a Foton-M mission, during which she mated, and produced 33 offspring after returning to Earth.

[124][125] In a 1750–1752 journal, Pehr Osbeck noted that cockroaches were frequently seen and found their way to the bakeries, after the sailing ship Gothenburg ran aground and was destroyed by rocks.

[126] Donald Harington's satirical novel The Cockroaches of Stay More (Harcourt, 1989) imagines a community of "roosterroaches" in a mythical Ozark town where the insects are named after their human counterparts.