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Cockroaches (or roaches) are
insect Insects (from Latin Latin (, or , ) is a classical language A classical language is a language A language is a structured system of communication Communication (from Latin ''communicare'', meaning "to share" or "to be in ...

insect
s of the order
Blattodea Blattodea is an order Order, ORDER or Orders may refer to: * Orderliness Orderliness is a quality that is characterized by a person’s interest in keeping their surroundings and themselves well organized, and is associated with other qualit ...

Blattodea
, which also includes
termite Termites are Eusociality, eusocial insects that are classified at the Taxonomy (biology), taxonomic rank of infraorder Isoptera, or alternatively as Taxonomic rank#All ranks, epifamily Termitoidae, within the order Blattodea (along with cockroa ...

termite
s. About 30 cockroach species out of 4,600 are associated with human habitats. Some species are well-known as
pest Pest or The Pest may refer to: Science and medicine * Pest (organism), an animal or plant detrimental to humans or human concerns ** Weed, a plant considered undesirable * Infectious disease, an illness resulting from an infection ** Plague (diseas ...
s. The cockroaches are an ancient group, with ancestors originating during the
Carboniferous The Carboniferous ( ) is a geologic period The geologic time scale (GTS) is a system of chronological dating that classifies Geology, geological strata (stratigraphy) in time. It is used by geologists, paleontology, paleontologists, and other ...
period, some 300-350 million years ago. Those early ancestors, however, lacked the internal
ovipositor The ovipositor is a tube-like organ (anatomy), organ used by some animals, especially insects, for the laying of Egg (biology), eggs. In insects, an ovipositor consists of a maximum of three pairs of appendages. The details and morphology of t ...
s of modern roaches. Cockroaches are somewhat generalized insects lacking special adaptations (such as the sucking
mouthparts
mouthparts
of
aphid Aphids are small sap-sucking insects and members of the Taxonomic rank, superfamily Aphidoidea. Common names include greenfly and blackfly, although individuals within a species can vary widely in color. The group includes the fluffy white Erio ...

aphid
s and other
true bugs Hemiptera (Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken in the area around Rome, known as Latium. Through the power of the Roman Re ...

true bugs
); they have chewing mouthparts and are likely among the most primitive of living
Neoptera Neoptera (Ancient Greek Ancient Greek includes the forms of the Greek language used in ancient Greece and the classical antiquity, ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycena ...
n insects. They are common and hardy insects capable of tolerating a wide range of
climates Climate is the long-term average of weather, typically averaged over a period of 30 years. More rigorously, it is the mean and variability of meteorological variables over a time spanning from months to millions of years. Some of the meteorologic ...
, from
Arctic The Arctic ( or ) is a polar regions of Earth, polar region located at the northernmost part of Earth. The Arctic consists of the Arctic Ocean, adjacent seas, and parts of Alaska (United States), Canada, Finland, Greenland (Danish Realm, ...

Arctic
cold to
tropical The tropics are the region of Earth surrounding the Equator. They are delimited in latitude by the Tropic of Cancer in the Northern Hemisphere at N and the Tropic of Capricorn in the Southern Hemisphere at S; these latitudes correspond to ...

tropical
heat. Tropical cockroaches are often much larger than temperate species. Contrary to popular belief, extinct cockroach relatives (
Blattoptera Blattoptera, or proto-cockroaches, is a name given to various "roachid" fossil insects related to cockroach Cockroaches (or roaches) are insects of the order Blattodea, which also includes termite Termites are Eusociality, eusocial insect ...
) and 'roachoids' such as the Carboniferous ''
Archimylacris ''Archimylacris'' (meaning "primitive ''Mylacris''", in reference to another species of Carboniferous cockroach) is an extinct genus of cockroach-like blattopterans, a group of insects ancestral to cockroaches, mantids, and termites. ''Archimyla ...
'' and the
Permian The Permian ( ) is a geologic period The geologic time scale (GTS) is a system of chronological dating that classifies Geology, geological strata (stratigraphy) in time. It is used by geologists, paleontology, paleontologists, and other earth ...
'' Apthoroblattina'' were not as large as the biggest modern species. Some species, such as the gregarious
German cockroach The German cockroach (''Blattella germanica'') is a small species of cockroach, typically about long. In color it varies from tan to almost black, and it has two dark, roughly parallel, streaks on the Prothorax, pronotum running Anatomical terms ...

German cockroach
, have an elaborate social structure involving common shelter, social dependence, information transfer and kin recognition. Cockroaches have appeared in human culture since
classical antiquity Classical antiquity (also the classical era, classical period or classical age) is the period of cultural history History (from Greek#REDIRECT Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, ...
. They are popularly depicted as dirty pests, although the majority of species are inoffensive and live in a wide range of habitats around the world.


Taxonomy and evolution

Cockroaches are members of the Superorder
Dictyoptera Dictyoptera (from Ancient Greek, Greek δίκτυον ''diktyon'' "net" and πτερόν ''pteron'' "wing") is an insect superorder that includes two extant Order (biology), orders of polyneopterous insects: the order Blattodea (termites and c ...
, which includes the
termite Termites are Eusociality, eusocial insects that are classified at the Taxonomy (biology), taxonomic rank of infraorder Isoptera, or alternatively as Taxonomic rank#All ranks, epifamily Termitoidae, within the order Blattodea (along with cockroa ...

termite
s and
mantid Mantidae is one of the largest family (biology), families in the Order (biology), order of Mantodea, praying mantises, based on the type species ''Mantis religiosa''; however, most genera are tropical or subtropical. Historically, this was the on ...
s, a group of insects once thought to be separate from cockroaches. Currently, 4,600 species and over 460 genera are described worldwide. The name "
cockroach Cockroaches (or roaches) are insects of the order Blattodea, which also includes termites. About 30 cockroach species out of 4,600 are associated with human habitats. Some species are well-known as Pest (organism), pests. The cockroaches are ...
" comes from the Spanish word for cockroach, ''cucaracha'', transformed by 1620s English
folk etymology Folk etymology (also known as popular etymology, analogical reformation, reanalysis, morphological reanalysis or etymological reinterpretation) is a change in a word or phrase resulting from the replacement of an unfamiliar form by a more famili ...
into "cock" and "roach". The scientific name derives from the Latin ''blatta'', "an insect that shuns the light", which in classical Latin was applied not only to cockroaches, but also to
mantids Mantidae is one of the largest families In human society, family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). Th ...
. Historically, the name Blattaria was used largely interchangeably with the name Blattodea, but whilst Blattaria was used to refer to 'true' cockroaches exclusively, the Blattodea also includes the termites. The current catalogue of world cockroach species uses the name Blattodea for the group. Another name,
Blattoptera Blattoptera, or proto-cockroaches, is a name given to various "roachid" fossil insects related to cockroach Cockroaches (or roaches) are insects of the order Blattodea, which also includes termite Termites are Eusociality, eusocial insect ...
, is also sometimes used to refer to extinct cockroach relatives. The earliest cockroach-like fossils ("blattopterans" or "roachids") are from the
Carboniferous The Carboniferous ( ) is a geologic period The geologic time scale (GTS) is a system of chronological dating that classifies Geology, geological strata (stratigraphy) in time. It is used by geologists, paleontology, paleontologists, and other ...
period 320 million years ago, as are fossil roachoid nymphs. According to one
hypothesis A hypothesis (plural hypotheses) is a proposed explanation An explanation is a set of statements usually constructed to describe a set of facts which clarifies the causes, context Context may refer to: * Context (language use), the rel ...
, cockroaches were an ancient group of insects that arose during the
Devonian The Devonian ( ) is a geologic period and system of the Paleozoic The Paleozoic (or Palaeozoic) Era ( ; from the Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the H ...
epoch In chronology 222px, Joseph Scaliger's ''De emendatione temporum'' (1583) began the modern science of chronology Chronology (from Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-E ...
. Fossil roachoids that lived during that time differ from modern cockroaches in that they had long external
ovipositor The ovipositor is a tube-like organ (anatomy), organ used by some animals, especially insects, for the laying of Egg (biology), eggs. In insects, an ovipositor consists of a maximum of three pairs of appendages. The details and morphology of t ...
s and are the ancestors of
mantis Mantises are an Order (biology), order (Mantodea) of insects that contains List of mantis genera and species, over 2,400 species in about 460 genera in 33 families. The largest family is the Mantidae ("mantids"). Mantises are distributed world ...

mantis
es, as well as modern cockroaches. As the body, hind wings and mouthparts are not preserved in fossils frequently, the relationship of these roachoids and modern cockroaches remains disputed. The first fossils of modern cockroaches with internal ovipositors appeared in the early
Cretaceous The Cretaceous ( ) is a geological period A geological period is one of the several subdivisions of geologic time enabling cross-referencing of rocks and geologic events from place to place. These periods form elements of a hierarchy of division ...

Cretaceous
. A recent phylogenetic analysis suggests that cockroaches originated at least in the
Jurassic The Jurassic ( ) is a geologic period The geologic time scale (GTS) is a system of chronological dating that classifies Geology, geological strata (stratigraphy) in time. It is used by geologists, paleontology, paleontologists, and other earth ...
. Common Mesozoic stem-group cockroaches include the Blattulidae and Mesoblattinidae. The evolutionary relationships of the Blattodea (cockroaches and termites) shown in the
cladogram A cladogram (from Greek#REDIRECT Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its population is appr ...

cladogram
are based on Inward, Beccaloni and Eggleton (2007). The cockroach families
Anaplectidae Anaplectidae is a family of cockroaches in the order Blattodea. Previously placed as a subfamily of the Ectobiidae there are presently (2020) two genera and more than 90 described species in Anaplectidae. Genera These two genera belong to the fa ...
,
Lamproblattidae Lamproblattidae is a small family of South and Central American cockroaches in the order Blattodea Blattodea is an order (biology), order of insects that contains cockroaches and termites. Formerly, the termites were considered a separate orde ...
, and
Tryonicidae The Tryonicidae are a family of cockroaches. Biodiversity and distribution Two genera containing 17 species are currently confirmed as belonging to this family. Table 1: Number of species of Tryonicidae in each region in which it is present (A ...
are not shown but are placed within the superfamily Blattoidea. The cockroach families
Corydiidae Corydiidae, previously known as Polyphagidae, is a family of the order Blattodea (cockroaches). Many are known as sand cockroaches. The family is divided into five subfamilies, comprising some 40 genera. One prominent species is the desert cockroac ...
and
Ectobiidae Ectobiidae (formerly Blattellidae) is a family of the order Blattodea (cockroaches). This family contains many of the smaller common household pest cockroaches, among others. They are sometimes called wood cockroaches. A few notable species includ ...
were previously known as the Polyphagidae and Blattellidae. Termites were previously regarded as a separate order
Isoptera Termites are eusocial insects that are classified at the taxonomic rank Taxonomy (general) is the practice and science of classification of things or concepts, including the principles that underlie such classification. The term may also re ...

Isoptera
to cockroaches. However, recent genetic evidence strongly suggests that they evolved directly from 'true' cockroaches, and many authors now place them as an " epifamily" of Blattodea. This evidence supported a hypothesis suggested in 1934 that termites are closely related to the wood-eating cockroaches (genus ''
Cryptocercus ''Cryptocercus'' is a genus of Dictyoptera (cockroaches and allies) and the sole member of its own family Cryptocercidae. Species are known as wood roaches or brown-hooded cockroaches. These roaches are subsocial, their young requiring considerabl ...
''). This hypothesis was originally based on similarity of the symbiotic gut
flagellate 's '' Artforms of Nature'', 1904 (''Giardia lamblia'') ('' Chlamydomonas'') A flagellate is a cell or organism with one or more whip-like Appendage, appendages called flagellum, flagella. The word ''flagellate'' also describes a particular const ...
s in termites regarded as
living fossil A living fossil is an extant taxon Neontology is a part of biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, ...
s and wood-eating cockroaches. Additional evidence emerged when F. A. McKittrick (1965) noted similar morphological characteristics between some termites and cockroach nymphs. The similarities among these cockroaches and termites have led some scientists to reclassify termites as a single family, the
Termitidae Termitidae is a family (biology), family of termites whose members are common name, commonly known as the higher termites. They are evolutionarily the most specialised termite group, with their gut having a high capacity to degrade lignocellulose. ...
, within the order Blattodea. Other scientists have taken a more conservative approach, proposing to retain the termites as the Termitoidae, an epifamily within the order. Such a measure preserves the classification of termites at family level and below.


Description

Most species of cockroach are about the size of a thumbnail, but several species are larger. The world's heaviest cockroach is the Australian
giant burrowing cockroach The giant burrowing cockroach (''Macropanesthia rhinoceros'') is also known as the rhinoceros cockroach, and Queensland giant cockroach. These cockroaches are native to Australia and mostly found in tropical and Subtropics, subtropical parts of Que ...
''Macropanesthia rhinoceros'', which can reach in length and weigh up to . Comparable in size is the Central American giant cockroach ''
Blaberus giganteus The Central American giant cave cockroach (''Blaberus giganteus''), also known as the Brazilian cockroach, is a cockroach Cockroaches (or roaches) are insects of the order Blattodea, which also includes termite Termites are Eusociali ...
''. The longest cockroach species is ''
Megaloblatta longipennis ''Megaloblatta'' is a genus of cockroaches in the family Ectobiidae. It includes the largest living species of cockroach, ''Megaloblatta longipennis'', which can grow to in length and have a wingspan of up to . ''Megaloblatta'', like many other ...
'', which can reach in length and across. A Central and South American species, ''
Megaloblatta blaberoides ''Megaloblatta'' is a genus of cockroach Cockroaches (or roaches) are insects of the order Blattodea, which also includes termite Termites are Eusociality, eusocial insects that are classified at the Taxonomy (biology), taxonomic rank o ...
'', has the largest wingspan of up to . At the other end of the size scale, ''
Attaphila ''Attaphila'' is a genus of cockroaches that live as Myrmecophily, myrmecophiles in the nests of Leafcutter ant, leaf-cutting ants. They have been suggested to feed on the fungus their host ants farm, or on the cuticular lipids of ant workers. '' ...
'' cockroaches that live with include some of the world's smallest species, growing to about 3.5 mm in length. Cockroaches are generalized insects with few special adaptations, and may be among the most
primitive Primitive may refer to: Mathematics * Primitive element (field theory) * Primitive element (finite field) * Primitive cell (crystallography) * Primitive notion, axiomatic systems * Primitive polynomial (disambiguation), one of two concepts * Primit ...
living
Neoptera Neoptera (Ancient Greek Ancient Greek includes the forms of the Greek language used in ancient Greece and the classical antiquity, ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycena ...
n insects. They have a relatively small head and a broad, flattened body, and most species are reddish-brown to dark brown. They have large
compound eye A compound eye is a visual organ found in arthropod An arthropod (, (gen. ποδός)) is an invertebrate animal having an exoskeleton, a Segmentation (biology), segmented body, and paired jointed appendages. Arthropods form the phylum Euart ...

compound eye
s, two
ocelli A simple eye (sometimes called a pigment pit) refers to a form of eye or an optical arrangement composed of a single lens and without an elaborate retina such as occurs in most vertebrates. In this sense "simple eye" is distinct from a multi-lense ...
, and long, flexible
antennae Antenna (pl. antennas or antennae) may refer to: Science and engineering * Antenna (radio), also known as an aerial, a transducer designed to transmit or receive electromagnetic (e.g., TV or radio) waves * Antennae Galaxies, the name of two coll ...
. The are on the underside of the head and include generalized chewing
mandibles In anatomy, the mandible, lower jaw or jawbone is the largest, strongest and lowest bone in the human facial skeleton. It forms the lower jaw and holds the lower tooth, teeth in place. The mandible sits beneath the maxilla. It is the only movable ...
,
salivary gland The salivary glands in mammal Mammals (from Latin Latin (, or , ) is a classical language A classical language is a language A language is a structured system of communication Communication (from Latin ''communicare'' ...
s and various touch and taste receptors. The body is divided into a thorax of three segments and a ten-segmented abdomen. The external surface has a tough
exoskeleton An exoskeleton (from Greek έξω, ''éxō'' "outer" and σκελετός, ''skeletós'' "skeleton") is the external skeleton A skeleton is a structural frame that supports an animal Animals (also called Metazoa) are multicellular ...

exoskeleton
which contains
calcium carbonate Calcium carbonate is a chemical compound A chemical compound is a chemical substance composed of many identical molecules (or molecular entity, molecular entities) composed of atoms from more than one chemical element, element held togethe ...

calcium carbonate
; this protects the inner organs and provides attachment to muscles. This external exoskeleton is coated with wax to repel water. The wings are attached to the second and third thoracic segments. The tegmina, or first pair of wings, are tough and protective; these lay as a shield on top of the membranous hind wings, which are used in flight. All four wings have branching longitudinal veins, as well as multiple cross-veins. The three pairs of legs are sturdy, with large coxae and five claws each. They are attached to each of the three thoracic segments. Of these, the front legs are the shortest and the hind legs the longest, providing the main propulsive power when the insect runs. 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. The structures have been used as inspiration for robotic legs. The abdomen has ten segments, each having a pair of spiracles for respiration. In addition to the spiracles, the final segment consists of a pair of cerci, a pair of anal styles, the anus and the external genitalia. Males have an
aedeagus An aedeagus (plural aedeagi) is a reproductive organ of male arthropod An arthropod (, (gen. ποδός)) is an invertebrate animal having an exoskeleton, a Segmentation (biology), segmented body, and paired jointed appendages. Arthropods form ...
through which they secrete sperm during copulation, while females have
spermatheca The spermatheca (pronounced plural: spermathecae ), also called receptaculum seminis (plural: receptacula seminis), is an organ Organ may refer to: Biology * Organ (anatomy) An organ is a group of Tissue (biology), tissues with similar f ...
for storing sperm and an
ovipositor The ovipositor is a tube-like organ (anatomy), organ used by some animals, especially insects, for the laying of Egg (biology), eggs. In insects, an ovipositor consists of a maximum of three pairs of appendages. The details and morphology of t ...
through which the are laid.


Distribution and habitat

Cockroaches are abundant throughout the world and live in a wide range of environments, especially in the
tropics The tropics are the region of Earth Earth is the third planet from the Sun and the only astronomical object known to harbour and support life. 29.2% of Earth's surface is land consisting of continents and islands. The remaining 70.8% ...

tropics
and
subtropics The subtropical zones or subtropics are geographical zone, geographical and Köppen climate classification, climate zones located to the north and south of the tropics, Torrid Zone. Geographically part of the Geographical zone#Temperate zones, ...

subtropics
. Cockroaches can withstand extremely low temperatures, allowing them to live in the
Arctic The Arctic ( or ) is a polar regions of Earth, polar region located at the northernmost part of Earth. The Arctic consists of the Arctic Ocean, adjacent seas, and parts of Alaska (United States), Canada, Finland, Greenland (Danish Realm, ...

Arctic
. Some species are capable of surviving temperatures of by manufacturing an antifreeze made out of
glycerol Glycerol (; also called glycerine in British English and glycerin in American English) is a simple polyol compound. It is a colorless, odorless, viscous liquid that is sweet-tasting and non-toxic. The glycerol backbone is found in lipids known ...
. In
North America North America is a continent A continent is any of several large landmasses. Generally identified by convention (norm), convention rather than any strict criteria, up to seven geographical regions are commonly regarded as continen ...

North America
, 50 species separated into five families are found throughout the continent. 450 species are found in
Australia Australia, officially the Commonwealth of Australia, is a Sovereign state, sovereign country comprising the mainland of the Australia (continent), Australian continent, the island of Tasmania, and numerous List of islands of Australia, sma ...

Australia
. Only about four widespread species are commonly regarded as pests. Cockroaches occupy a wide range of habitats. Many live in
leaf litter Litterfall, plant litter, leaf litter, tree litter, soil litter, or duff, is dead plant Plants are predominantly photosynthetic Photosynthesis is a process used by plants and other organisms to Energy transformation, convert light ene ...

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. Some live in arid regions and have developed mechanisms to survive without access to water sources. Others are aquatic, living near the surface of water bodies, including
bromeliad The Bromeliaceae (the bromeliads) is a family In human society A society is a Social group, group of individuals involved in persistent Social relation, social interaction, or a large social group sharing the same spatial or socia ...

bromeliad
phytotelma The giant pitchers of '' Nepenthes rajah'' act as phytotelmata Phytotelma (plural phytotelmata) is a small water-filled cavity in a terrestrial plant. The water accumulated within these plants may serve as the habitat for associated fauna and fl ...
ta, and diving to forage for food. Most of these respire by piercing the water surface with the tip of the abdomen which acts as a , but some carry a bubble of air under their thoracic shield when they submerge. Others live in the
forest canopy A forest is an area of land dominated by tree In botany, a tree is a perennial plant with an elongated Plant stem, stem, or trunk (botany), trunk, supporting branches and leaves in most species. In some usages, the definition of a t ...
where they may be one of the main types of
invertebrate Invertebrates are animals that neither possess nor develop a vertebral column (commonly known as a ''backbone'' or ''spine''), derived from the notochord. This includes all animals apart from the chordata, chordate subphylum vertebrate, Vertebra ...
present. Here they may hide during the day in crevices, among dead leaves, in bird and insect nests or among
epiphyte An epiphyte is an organism that grows on the surface of a plant and derives its moisture and nutrients from the air, rain, water (in marine environments) or from debris accumulating around it. Epiphytes take part in nutrient cycles and add to both ...

epiphyte
s, emerging at night to feed.


Behavior

Cockroaches are social insects; a large number of species are either
gregarious Sociality is the degree to which individuals in an animal Animals (also called Metazoa) are multicellular eukaryotic organisms that form the Kingdom (biology), biological kingdom Animalia. With few exceptions, animals Heterotroph, consum ...
or inclined to aggregate, and a slightly smaller number exhibit parental care. It used to be thought that cockroaches aggregated because they were reacting to environmental cues, but it is now believed that
pheromone A pheromone (from Ancient Greek Ancient Greek includes the forms of the Greek language Greek ( el, label=Modern Greek Modern Greek (, , or , ''Kiní Neoellinikí Glóssa''), generally referred to by speakers simply as Greek (, ...

pheromone
s are involved in these behaviors. Some species secrete these in their feces with gut microbial
symbionts Symbiosis (from Greek , , "living together", from , , "together", and , bíōsis, "living") is any type of a close and long-term biological interaction In ecology Ecology (from el, οἶκος, "house" and el, -λογία, label=none, ...

symbionts
being involved, while others use glands located on their mandibles. Pheromones produced by the cuticle may enable cockroaches to distinguish between different populations of cockroach by odor. The behaviors involved have been studied in only a few species, but German cockroaches leave fecal trails with an odor gradient. Other cockroaches follow such trails to discover sources of food and water, and where other cockroaches are hiding. Thus, cockroaches have
emergent behavior In philosophy Philosophy (from , ) is the study of general and fundamental questions, such as those about reason, Metaphysics, existence, Epistemology, knowledge, Ethics, values, Philosophy of mind, mind, and Philosophy of language, ...
, in which group or
swarm behavior Swarm behaviour, or swarming, is a collective animal behaviour, collective behaviour exhibited by entities, particularly animals, of similar size which aggregate together, perhaps milling about the same spot or perhaps moving ''en masse'' or ani ...
emerges from a simple set of individual interactions. Daily rhythms may also be regulated by a complex set of hormonal controls of which only a small subset have been understood. 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 rhythm A circadian rhythm (), or circadian cycle, is a natural, internal process that regulates the sleep–wake cycle and repeats roughly every 24 hours. It can refer to any process that originates within an organism (i.e., endogenous Endogenous subst ...

circadian rhythm
s of the cockroach. Pest species adapt readily to a variety of environments, but prefer warm conditions found within buildings. Many tropical species prefer even warmer environments. Cockroaches are mainly
nocturnal Nocturnality is an animal behavior Ethology is the scientific Science (from the Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was origina ...
and run away when exposed to light. An exception to this is the Asian cockroach, which flies mostly at night but is attracted to brightly lit surfaces and pale colors.


Collective decision-making

Gregarious cockroaches display collective decision-making when choosing food sources. 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. Other mathematical models have been developed to explain aggregation dynamics and conspecific recognition. Cooperation and competition are balanced in cockroach group decision-making behavior. Cockroaches appear to use just two pieces of information to decide where to go, namely how dark it is and how many other cockroaches there are. A study used specially-scented roach-sized robots that seem real to the roaches to demonstrate that once there are enough insects in a place to form a
critical mass In nuclear engineering Nuclear engineering is the branch of engineering Engineering is the use of scientific method, scientific principles to design and build machines, structures, and other items, including bridges, tunnels, roads, ...
, the roaches accepted the collective decision on where to hide, even if this was an unusually lit place.


Social behavior

When reared in isolation, German cockroaches show behavior that is different from behavior when reared in a group. 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 took longer to recognize receptive females. Because these changes occurred in many contexts, the authors suggested them as constituting a behavioral syndrome. These effects might have been due either to reduced metabolic and developmental rates in isolated individuals or the fact that the isolated individuals had not had a training period to learn about what others were like via their antennae. Individual
American cockroach The American cockroach (''Periplaneta americana'') is the largest species of common cockroach, and often considered a pest Pest or The Pest may refer to: Science and medicine * Pest (organism), an animal or plant detrimental to humans or human co ...

American cockroach
es appear to have consistently different "personalities" regarding how they seek shelter. In addition, group personality is not simply the sum of individual choices, but reflects conformity and collective decision-making. The gregarious German and American cockroaches have elaborate social structure, chemical signalling, and "social herd" characteristics. Lihoreau and his fellow researchers stated: There is evidence that a few species of group-living roaches in the genera '' Melyroidea'' and '' Aclavoidea'' may exhibit a reproductive division of labor, which, if confirmed, would make these the only genuinely
eusocial Eusociality (from Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its population is approximately 10.7 mil ...
lineage known among roaches, in contrast to the
subsocial Sociality is the degree to which individuals in an animal population tend to associate in social groups (gregariousness) and form cooperative societies. Sociality is a survival response to evolutionary pressures. For example, when a mother wasp ...
members of the genus ''
Cryptocercus ''Cryptocercus'' is a genus of Dictyoptera (cockroaches and allies) and the sole member of its own family Cryptocercidae. Species are known as wood roaches or brown-hooded cockroaches. These roaches are subsocial, their young requiring considerabl ...
''.


Sounds

Some species make a buzzing noise while other cockroaches make a chirping noise. '' Gromphadorhina'' species and '' Archiblatta hoeveni'' produce sound through the modified spiracles on the fourth abdominal segment. In the former species, several different hisses are produced, including disturbance sounds, produced by adults and larger nymphs; and aggressive, courtship and copulatory sounds produced by adult males. '' Henschoutedenia epilamproides'' has a stridulatory organ between its thorax and abdomen, but the purpose of the sound produced is unclear. Several Australian species practice acoustic and vibration behaviour as an aspect of courtship. They have been observed producing hisses and whistles from air forced through the spiracles. Furthermore, in the presence of a potential mate, some cockroaches tap the substrate in a rhythmic, repetitive manner. Acoustic signals may be of greater prevalence amongst perching species, particularly those that live on low vegetation in Australia's tropics.


Biology


Digestive tract

Cockroaches are generally
omnivorous An omnivore () is an animal Animals (also called Metazoa) are multicellular A multicellular organism is an organism In biology, an organism () is any organic, life, living system that functions as an individual entity. Al ...
; the American cockroach (''Periplaneta americana''), for example, feeds on a great variety of foodstuffs including bread, fruit, leather, starch in book bindings, paper, glue, skin flakes, hair, dead insects and soiled clothing. Many species of cockroach harbor in their gut
symbiotic Symbiosis (from Ancient Greek, Greek , , "living together", from , , "together", and , bíōsis, "living") is any type of a close and long-term biological interaction between two different Organism, biological organisms, be it Mutualism (biolog ...

symbiotic
protozoa Protozoa (singular protozoon or protozoan, plural protozoa or protozoans) is an informal term for a group of single-celled eukaryote Eukaryotes () are organism In biology, an organism () is any organic, life, living system that ...

protozoa
ns and
bacteria Bacteria (; common noun bacteria, singular bacterium) are ubiquitous, mostly free-living organisms often consisting of one Cell (biology), biological cell. They constitute a large domain (biology), domain of prokaryotic microorganisms. Typ ...

bacteria
which are able to digest
cellulose Cellulose is an organic compound In chemistry Chemistry is the study of the properties and behavior of . It is a that covers the that make up matter to the composed of s, s and s: their composition, structure, properties, behavior ...

cellulose
. In many species, these symbionts may be essential if the insect is to utilize cellulose; however, some species secrete
cellulase Cellulase is any of several enzymes Enzymes () are proteins that act as biological catalysts (biocatalysts). Catalysts accelerate chemical reactions. The molecules upon which enzymes may act are called substrate (chemistry), substrates, a ...
in their
saliva Saliva (commonly referred to as spit) is an extracellular fluid In cell biology Cell biology (also cellular biology or cytology) is a branch of biology Biology is the natural science that studies life and living organisms, including t ...
, and the wood-eating cockroach, '' Panesthia cribrata'', is able to survive indefinitely on a diet of crystallized cellulose while being free of microorganisms. The similarity of these symbionts in the genus ''
Cryptocercus ''Cryptocercus'' is a genus of Dictyoptera (cockroaches and allies) and the sole member of its own family Cryptocercidae. Species are known as wood roaches or brown-hooded cockroaches. These roaches are subsocial, their young requiring considerabl ...
'' to those in termites are such that these cockroaches have been suggested to be more closely related to termites than to other cockroaches, and current research strongly supports this hypothesis about their relationships. All species studied so far carry the obligate Mutualism (biology), mutualistic endosymbiont bacterium ''Blattabacterium'', with the exception of ''Nocticola'', an Australian cave-dwelling genus without eyes, pigment or wings, which recent genetic studies indicate is a very primitive cockroach. It had previously been thought that all five families of cockroach were descended from a common ancestor that was infected with ''Blattabacterium cuenoti, B. cuenoti''. It may be that ''N. australiensis'' subsequently lost its symbionts, or alternatively this hypothesis will need to be re-examined.


Tracheae and breathing

Like other insects, cockroaches breathe through a system of tubes called Invertebrate trachea, tracheae which are attached to openings called spiracles on all body segments. When the carbon dioxide level in the insect rises high enough, valves on the spiracles open and carbon dioxide Diffusion, diffuses out and oxygen diffuses in. The tracheal system branches repeatedly, the finest tracheoles bringing air directly to each cell (biology), cell, allowing gaseous exchange to take place. 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.


Reproduction

Cockroaches use
pheromone A pheromone (from Ancient Greek Ancient Greek includes the forms of the Greek language Greek ( el, label=Modern Greek Modern Greek (, , or , ''Kiní Neoellinikí Glóssa''), generally referred to by speakers simply as Greek (, ...

pheromone
s to attract mates, and the males practice courtship rituals, such as posturing and stridulation. Like many insects, cockroaches mate facing away from each other with their genitalia in contact, and copulation can be prolonged. A few species are known to be parthenogenesis, parthenogenetic, reproducing without the need for males. Female cockroaches are sometimes seen carrying egg cases on the end of their abdomens; the German cockroach holds about 30 to 40 long, thin eggs in a case called an ootheca. She drops the capsule prior to hatching, though live births do occur in rare instances. The egg capsule may take more than five hours to lay and is initially bright white in color. The eggs are hatched from the combined pressure of the hatchlings gulping air. The hatchlings are initially bright white nymph (biology), nymphs and continue inflating themselves with air, becoming harder and darker within about four hours. Their transient white stage while hatching and later while ecdysis, molting has led to claims of albino cockroaches. Development from eggs to adults takes three to four months. Cockroaches live up to a year, and the female may produce up to eight egg cases in a lifetime; in favorable conditions, she can produce 300 to 400 offspring. Other species of cockroaches, however, can produce far more eggs; in some cases a female needs to be impregnated only once to be able to lay eggs for the rest of her life. The female usually attaches the egg case to a substrate, inserts it into a suitably protective crevice, or carries it about until just before the eggs hatch. Some species, however, are ovoviviparous, keeping the eggs inside their body, with or without an egg case, until they hatch. At least one genus, ''Diploptera'', is fully viviparous. Cockroaches have incomplete metamorphosis, meaning that the nymph (biology), nymphs are generally similar to the adults, except for undeveloped wings and genitalia. Development is generally slow, and may take a few months to over a year. The adults are also long-lived; some have survived for as many as four years in the laboratory. File:Cockroach nymph australia.jpg, 3 millimeter cockroach nymph File:Cockroach egglaying 1.jpg, Female ''Periplaneta fuliginosa'' with ootheca File:Old Ootheca.jpg, Empty ootheca File:Periplaneta-americana-Eier.jpg, American cockroach oothecae


Hardiness

Cockroaches are among the hardiest insects. 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. Some can go without air for 45 minutes. Japanese cockroach (''Periplaneta japonica'') nymph (biology), nymphs, which hibernate in cold winters, have survived twelve hours at in laboratory experiments. Experiments on decapitated specimens of several species of cockroach found a variety of behavioral functionality remained, including shock avoidance and escape behavior, although many insects other than cockroaches are also able to survive decapitation, and popular claims of the longevity of headless cockroaches do not appear to be based on published research. The severed head is able to survive and wave its antennae for several hours, or longer when refrigerated and given nutrients. It is urban legend, popularly suggested that cockroaches will "inherit the earth" if humanity destroys itself in a nuclear warfare, nuclear war. 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 Drosophila melanogaster, fruit fly. The cockroach's ability to withstand radiation has been explained through the cell cycle. Cells are most vulnerable to the effects of radiation while they are dividing. A cockroach's cells divide only once each molting cycle (which is weekly, for the juvenile German cockroach). Since not all cockroaches would be molting at the same time, many would be unaffected by an acute burst of radiation, although lingering and more acute radiation would still be harmful.


Relationship with humans


In research and education

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. The cockroach is a convenient insect to study as it is large and simple to raise in a laboratory environment. This makes it suitable both for research and for school and undergraduate biology studies. It can be used in experiments on topics such as learning, sexual
pheromone A pheromone (from Ancient Greek Ancient Greek includes the forms of the Greek language Greek ( el, label=Modern Greek Modern Greek (, , or , ''Kiní Neoellinikí Glóssa''), generally referred to by speakers simply as Greek (, ...

pheromone
s, spatial orientation, aggression, activity rhythms and the Circadian clock, biological clock, and behavioral ecology. Research conducted in 2014 suggests that humans fear cockroaches the most, even more than mosquitoes, due to an evolutionary aversion.


As pests

The Blattodea include some thirty species of cockroaches associated with humans; these species are atypical of the thousands of species in the order. They feed on human and pet food and can leave an offensive odor. They can passively transport pathogenic microbes on their body surfaces, particularly in environments such as hospitals. Cockroaches are linked with allergic reactions in humans. One of the proteins that trigger allergic reactions is tropomyosin, which can cause cross-reactive allergy to house dust mites, dust mites and shrimp. These allergens are also linked with asthma. About 60% of asthma patients in Chicago are also sensitive to cockroach allergens. Studies similar to this have been done globally and all the results are similar. Some species of cockroach can live for up to a month without food, so just because no cockroaches are visible in a home does not mean that they are not there. Approximately 20–48% of homes with no visible sign of cockroaches have detectable cockroach allergens in dust.


Control

Many remedies have been tried in the search for control of the major pest species of cockroaches, which are resilient and fast-breeding. Household chemicals like sodium bicarbonate (baking soda) have been suggested, without evidence for their effectiveness. Garden herbs including bay leaves, bay, catnip, Mentha, mint, cucumber, and garlic have been proposed as repellents. Poisoned bait containing hydramethylnon or fipronil, and boric acid powder is effective on adults. Baits with egg killers are also quite effective at reducing the cockroach population. Alternatively, insecticides containing deltamethrin or pyrethrin are very effective. In Singapore and Malaysia, taxi drivers use Pandanus amaryllifolius, pandan leaves to repel cockroaches in their vehicles. A natural control of pest cockroaches has been advanced by several published studies. The mold Metharhizium anisopliae is an entomopathogenic fungus that has several strains, which have been selected to selectively kill particular species of cockroach. The fungal spores can be incorporated into baited traps which spread the fungus to individuals who spread the fungus more widely. It is best used in enclosed spaces such as mothballed naval ships or buildings which are in complete control by one owner. Some parasites and predators are effective for biological control of cockroaches. Parasitoidal wasps such as ''Ampulex'' wasps sting nerve ganglia in the cockroach's thorax, causing temporary paralysis and allowing the wasp to deliver an incapacitating sting into the cockroach's brain. The wasp clips the antennae with its mandibles and drinks some hemolymph before dragging the prey to a burrow, where an egg (rarely two) is laid on it. The wasp larva feeds on the subdued living cockroach. Another wasp considered to be a promising candidate for biological control is the ensign wasp ''Evania appendigaster'', which attacks cockroach oothecae to lay a single egg inside. Ongoing research is still developing technologies allowing for mass-rearing these wasps for application releases. Latrodectus, Widow spiders commonly prey on cockroaches though their venomous bite introduces its own problems for humans and pets. Cockroaches can be trapped in a deep, smooth-walled jar baited with food inside, placed so that cockroaches can reach the opening, for example with a ramp of card or twigs on the outside. An inch or so of water or stale beer (by itself a cockroach attractant) in the jar can be used to drown any insects thus captured. The method works well with the American cockroach, but less so with the German cockroach. A study conducted by scientists at Purdue University concluded that the most common cockroaches in the United States, US,
Australia Australia, officially the Commonwealth of Australia, is a Sovereign state, sovereign country comprising the mainland of the Australia (continent), Australian continent, the island of Tasmania, and numerous List of islands of Australia, sma ...

Australia
and Europe were able to develop a “cross resistance” to multiple types of pesticide. This contradicted previous understanding that the animals can develop resistance against one pesticide at a time. 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.


As food

Although considered disgusting in Western culture, cockroaches are eaten in many places around the world.Marion Copeland [2004]
Cockroach
(Pages 86 to 88). Published by Reaktion Books
Whereas household pest cockroaches may carry bacteria and viruses, cockroaches bred under laboratory conditions can be used to prepare nutritious food. In Thailand and Mexico, the heads and legs are removed, and the remainder may be boiled, sautéed, grilled, dried or diced. In China, cockroaches have become popular as medicine and cockroach farming is rising with over 100 farms. The cockroaches are fried twice in a wok of hot oil, which makes them crispy with soft innards that are like cottage cheese. Fried cockroaches are ground and sold as pills for stomach, heart and liver diseases. A cockroach recipe from Taiwan, Formosa (Taiwan) specifies salting and frying cockroaches after removing the head and entrails.Richard Schweid [2015]
The Cockroach Papers: A Compendium of History and Lore
(Page 69). Published by University of Chicago Press.


In traditional medicine

In China, cockroaches are raised in large quantities for medicinal purposes.


Conservation

While a small minority of cockroaches are associated with human habitats and viewed as repugnant by many people, a few species are of conservation concern. The Lord Howe Island wood-feeding cockroach (''Panesthia lata'') is listed as endangered by the New South Wales Scientific Committee, but the cockroach may be extinct on Lord Howe Island itself. The introduction of rats, the spread of Rhodes grass (''Chloris gayana'') and fires are possible reasons for their scarcity. Two species are currently listed as Endangered species, endangered and critically endangered by the IUCN Red List, ''Delosia ornata'' and ''Nocticola gerlachi''. Both cockroaches have a restricted distribution and are threatened by habitat loss and sea level rise, rising sea levels. Only 600 ''Delosia ornata'' adults and 300 nymphs are known to exist, and these are threatened by a hotel development. No action has been taken to save the two cockroach species, but protecting their natural habitats may prevent their extinction. In the former Soviet Union, cockroach populations have been declining at an alarming rate; this may be exaggerated, or the phenomenon may be temporary or cyclic. One species of roach, ''Simandoa conserfariam'', is considered extinct in the wild.


Cultural depictions

Cockroaches were known and considered repellent but medicinally useful in Classical times. An insect named in Greek "σίλφη" (''silphe'') has been identified with the cockroach, though the scientific name ''Silpha'' refers to a genus of carrion beetles. It is mentioned by Aristotle, saying that it sheds its skin; it is described as foul-smelling in Aristophanes' play ''Peace (play), Peace''; Euenus called it a pest of book collections, being "page-eating, destructive, black-bodied" in his ''Analect''. Virgil named the cockroach "Lucifuga" ("one that avoids light"). 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. Pedanius Dioscorides, Dioscorides recorded the use of the "Silphe", ground up with oil, as a remedy for earache. Lafcadio Hearn (1850–1904) asserted that "For tetanus cockroach tea is given. I do not know how many cockroaches go to make up the cup; but I find that faith in this remedy is strong among many of the American population of New Orleans. A poultice of boiled cockroaches is placed over the wound." He adds that cockroaches are eaten, fried with garlic, for indigestion. Several cockroach species, such as ''Blaptica dubia'', are raised as food for insectivorous pets. A few cockroach species are raised as pets, most commonly the giant Madagascar hissing cockroach, ''Gromphadorhina portentosa''. Whilst the hissing cockroaches may be the most commonly kept species, there are many species that are kept by cockroach enthusiasts; there is even a specialist society: the Blattodea Culture Group (BCG), which was a thriving organisation for about 15 years although now appears to be dormant. The BCG provided a source of literature for people interested in rearing cockroaches which was otherwise limited to either scientific papers, or general insect books, or books covering a variety of exotic pets; in the absence of an inclusive book one member published ''Introduction to Rearing Cockroaches'' which still appears to be the only book dedicated to rearing cockroaches. Cockroaches have been used for space tests. A cockroach given the name Nadezhda (cockroach), Nadezhda was sent into space by Russian scientists as part of a Foton (satellite)#Foton-M, Foton-M mission, during which she mated, and later became the first terrestrial animal to produce offspring that had been conceived in space. Because of their long association with humans, cockroaches are frequently referred to in popular culture. In Western culture, cockroaches are often depicted as dirty pests. In a 1750–1752 journal, Peter 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. Donald Harington (writer), 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. Madonna (entertainer), Madonna has famously quoted, "I am a survivor. I am like a cockroach, you just can't get rid of me." An urban legend maintains that cockroaches are radiation-resistant, and thus would survive a nuclear war.


References


External links


Cockroach Species File
Online world catalogue of cockroaches.

chapter in United States Environmental Protection Agency and UF/IFAS National Public Health Pesticide Applicator Training Manual
''Cockroach Studies'' journal
(ISSN 1862-6491) {{DEFAULTSORT:Cockroach Cockroaches, Cockroaches Household pest insects Insect common names Insects in culture