The German cockroach (''Blattella germanica''), colloquially known as the croton bug, is a
species
A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...
of small
cockroach
Cockroaches (or roaches) are insects belonging to the Order (biology), order Blattodea (Blattaria). About 30 cockroach species out of 4,600 are associated with human habitats. Some species are well-known Pest (organism), pests.
Modern cockro ...
, typically about
long. In color it varies from tan to almost black, and it has two dark, roughly parallel, streaks on the
pronotum
The prothorax is the foremost of the three segments in the thorax of an insect, and bears the first pair of legs. Its principal sclerites (exoskeletal plates) are the pronotum (dorsal), the prosternum (ventral), and the propleuron (lateral) on e ...
running
anteroposteriorly from behind the head to the base of the wings. Although ''B. germanica'' has wings, it can barely fly, although it may glide when disturbed.
Of the few species of cockroach that are domestic
pests
PESTS was an anonymous American activist group formed in 1986 to critique racism, tokenism, and exclusion in the art world. PESTS produced newsletters, posters, and other print material highlighting examples of discrimination in gallery represent ...
, it probably is the most widely troublesome example.
It is very closely related to the
Asian cockroach, and to the casual observer, the two appear nearly identical and may be mistaken for each other.
History
Previously thought to be a native of Europe, the German cockroach later was considered to have emerged from the region of
Ethiopia
Ethiopia, officially the Federal Democratic Republic of Ethiopia, is a landlocked country located in the Horn of Africa region of East Africa. It shares borders with Eritrea to the north, Djibouti to the northeast, Somalia to the east, Ken ...
in Northeast Africa,
but recent evidence indicates that it actually originated in South Asia or Southeast Asia, and diverged from ''
Blattella asahinai
''Blattella asahinai'', the Asian cockroach, is a species of cockroach that was first described in 1981 from insects collected on Okinawa Island, Japan.
It is a small species of cockroach, typically long and tan to dark brown in colour with d ...
'' slightly over 2000 years ago. The cockroach's sensitivity to cold might reflect its origin from such warm climates, and its spread as a
domiciliary pest since ancient times has resulted from incidental human transport and shelter. The species now is
cosmopolitan
Cosmopolitan may refer to:
Internationalism
* World citizen, one who eschews traditional geopolitical divisions derived from national citizenship
* Cosmopolitanism, the idea that all of humanity belongs to a single moral community
* Cosmopolitan ...
in distribution, occurring as a household pest on all continents except Antarctica, and on many major islands, as well. It accordingly has been given various names in the cultures of many regions.
Biology and pest status
The German cockroach occurs widely in human buildings, but is particularly associated with
restaurant
A restaurant is an establishment that prepares and serves food and drinks to customers. Meals are generally served and eaten on the premises, but many restaurants also offer take-out and Delivery (commerce), food delivery services. Restaurants ...
s,
food processing
Food processing is the transformation of agricultural products into food, or of one form of food into other forms. Food processing takes many forms, from grinding grain into raw flour, home cooking, and complex industrial methods used in the mak ...
facilities,
hotel
A hotel is an establishment that provides paid lodging on a short-term basis. Facilities provided inside a hotel room may range from a modest-quality mattress in a small room to large suites with bigger, higher-quality beds, a dresser, a re ...
s, and institutional establishments such as
nursing home
A nursing home is a facility for the residential care of older people, senior citizens, or disabled people. Nursing homes may also be referred to as care homes, skilled nursing facilities (SNF), or long-term care facilities. Often, these terms ...
s and
hospital
A hospital is a healthcare institution providing patient treatment with specialized Medical Science, health science and auxiliary healthcare staff and medical equipment. The best-known type of hospital is the general hospital, which typically ...
s. They can survive outside as well, though they are not commonly found in the wild.
In cold climates, they occur only near human dwellings, because they cannot survive severe cold. However, German cockroaches have been found as
inquiline
In zoology, an inquiline (from Latin ''inquilinus'', "lodger" or "tenant") is an animal that lives commensally in the nest, burrow, or dwelling place of an animal of another species. For example, some organisms, such as insects, may live in the ...
s ("tenants") of human buildings as far north as
Alert, Nunavut
Alert, in the Qikiqtaaluk Region of Nunavut, Canada, is the northernmost continuously inhabited place in the world. The location is on Ellesmere Island (in the Queen Elizabeth Islands) at latitude 82°30'05" north, from the North Pole. It tak ...
. Similarly, they have been found as far south as southern
Patagonia
Patagonia () is a geographical region that includes parts of Argentina and Chile at the southern end of South America. The region includes the southern section of the Andes mountain chain with lakes, fjords, temperate rainforests, and glaciers ...
.
Though
nocturnal
Nocturnality is a ethology, behavior in some non-human animals characterized by being active during the night and sleeping during the day. The common adjective is "nocturnal", versus diurnality, diurnal meaning the opposite.
Nocturnal creatur ...
, the German cockroach occasionally appears by day, especially if the population is crowded or has been disturbed. However, sightings are most frequent in the evening, when someone suddenly brings a light into a room deserted after dark, such as a kitchen where they have been scavenging.
When excited or frightened, the species emits an unpleasant odor.
Diet
German cockroaches are
omnivorous
An omnivore () is an animal that regularly consumes significant quantities of both plant and animal matter. Obtaining energy and nutrients from plant and animal matter, omnivores digest carbohydrates, protein, fat, and fiber, and metabolize ...
scavenger
Scavengers are animals that consume Corpse decomposition, dead organisms that have died from causes other than predation or have been killed by other predators. While scavenging generally refers to carnivores feeding on carrion, it is also a he ...
s. They are attracted particularly to meats,
starch
Starch or amylum is a polymeric carbohydrate consisting of numerous glucose units joined by glycosidic bonds. This polysaccharide is produced by most green plants for energy storage. Worldwide, it is the most common carbohydrate in human diet ...
es, sugars, and fatty foods. Where a shortage of foodstuff exists, they may eat household items such as
soap
Soap is a salt (chemistry), salt of a fatty acid (sometimes other carboxylic acids) used for cleaning and lubricating products as well as other applications. In a domestic setting, soaps, specifically "toilet soaps", are surfactants usually u ...
,
glue
Adhesive, also known as glue, cement, mucilage, or paste, is any non-metallic substance applied to one or both surfaces of two separate items that binds them together and resists their separation.
The use of adhesives offers certain advantage ...
, and
toothpaste
Toothpaste is a paste or gel dentifrice that is used with a toothbrush to clean and maintain the aesthetics of Human tooth, teeth. Toothpaste is used to promote oral hygiene: it is an abrasive that aids in removing dental plaque and food from th ...
. In famine conditions, they turn cannibalistic, chewing at each other's wings and legs.
The German cockroach is an
intermediate host
In biology and medicine, a host is a larger organism that harbours a smaller organism; whether a parasitic, a mutualistic, or a commensalist ''guest'' (symbiont). The guest is typically provided with nourishment and shelter. Examples include ...
of the
Acanthocephala
Acanthocephala ( Greek , ' 'thorn' + , ' 'head') is a group of parasitic worms known as acanthocephalans, thorny-headed worms, or spiny-headed worms, characterized by the presence of an eversible proboscis, armed with spines, which it uses t ...
n parasite ''
Moniliformis kalahariensis
''Moniliformis'' is a genus of parasitic worms in the Acanthocephala phylum.
Taxonomy
Genetic analysis has been conducted on four species: ''Moniliformis moniliformis'', ''M. saudi'', ''M. cryptosaudi'' and ''M. kalahariensis''. Based on these r ...
''.
Reproduction
The German cockroach reproduces faster than any other residential cockroach,
growing from egg to reproductive adult in roughly 50 – 60 days under ideal conditions.
Females are rounder and shorter in contrast to males which tend to be longer, narrower and of lighter color. Once fertilized, a female German cockroach develops an
ootheca
An ootheca (: oothecae ) is a type of egg capsule made by any member of a variety of species including mollusks (such as '' Turbinella laevigata''), mantises, and cockroaches.
Etymology
The word is a Latinized combination of ''oo-'', meaning " ...
in her abdomen. The abdomen swells as her eggs develop, until the translucent tip of the ootheca begins to protrude from the end of her abdomen, and by that time the eggs inside are fully sized, about 1/4 inch long with 16 segments.
The ootheca, at first translucent, soon turns white and then within a few hours turns pink, progressively darkening until, some 48 hours later, it attains the dark red-brown of the shell of a chestnut. It has a keel-like ridge along the line where the young emerge, and curls slightly towards that edge as it completes its maturation. A small percentage of the nymphs may hatch while the ootheca is still attached to the female, but the majority emerge some 24 hours after it has detached from the female's body. The newly hatched 3-mm-long black nymphs then progress through six or seven
instar
An instar (, from the Latin '' īnstar'' 'form, likeness') is a developmental stage of arthropods, such as insects, which occurs between each moult (''ecdysis'') until sexual maturity is reached. Arthropods must shed the exoskeleton in order to ...
s before becoming sexually mature, but
ecdysis
Ecdysis is the moulting of the cuticle in many invertebrates of the clade Ecdysozoa. Since the cuticle of these animals typically forms a largely inelastic exoskeleton, it is shed during growth and a new, larger covering is formed. The remnant ...
is such a hazardous process that nearly half the nymphs die of natural causes before reaching adulthood. Molted skins and dead nymphs are soon eaten by living nymphs present at the time of molting.
Pest control
The German cockroach is very successful at establishing an
ecological niche
In ecology, a niche is the match of a species to a specific environmental condition.
Three variants of ecological niche are described by
It describes how an organism or population responds to the distribution of Resource (biology), resources an ...
in buildings, and is resilient in the face of many
pest-control
Pest control is the regulation or management of a species defined as a pest; such as any animal, plant or fungus that impacts adversely on human activities or environment. The human response depends on the importance of the damage done and wi ...
measures. Reasons include:
* lack of natural
predator
Predation is a biological interaction in which one organism, the predator, kills and eats another organism, its prey. It is one of a family of common List of feeding behaviours, feeding behaviours that includes parasitism and micropredation ...
s in a human habitat
* prolific reproduction
* short reproductive cycle
* the ability to hide in very small refuges
* sexual maturity attained within several weeks, and
* adaptation and resistance to some
chemical pesticides
Pesticides are substances that are used to control pests. They include herbicides, insecticides, nematicides, fungicides, and many others (see table). The most common of these are herbicides, which account for approximately 50% of all pesti ...
The German cockroach is resistant to 42 active ingredients from most major groups of synthetic
insecticide
Insecticides are pesticides used to kill insects. They include ovicides and larvicides used against insect eggs and larvae, respectively. The major use of insecticides is in agriculture, but they are also used in home and garden settings, i ...
s such as organochlorides,
organophosphate
In organic chemistry, organophosphates (also known as phosphate esters, or OPEs) are a class of organophosphorus compounds with the general structure , a central phosphate molecule with alkyl or aromatic substituents. They can be considered ...
s, carbamates, synthetic pyrethroids, neonicotinoids, oxadiazines, and phenyl pyrazoles.
German cockroach resistance was first observed with
chlordane
Chlordane, or chlordan, is an organochlorine compound that was used as a pesticide. It is a white solid. In the United States, chlordane was used for termite-treatment of approximately 30 million homes until it was banned in 1988. Chlordane was b ...
in 1952. Because German cockroaches have a very high number of genes, they can adapt and evolve resistance to pesticides. They also have many receptors for smell and can sense new food sources.
German cockroaches are
thigmotactic
Thigmotaxis (from Greek ''thigma'', "touch" meaning contact with an object, and ''taxis'', "arrangement, order", meaning reaction by movement) is a behavioral response to tactile stimuli, typically referring to an organism's movement in response t ...
, meaning they prefer confined spaces, and they are small compared to other pest species, so they can hide within small cracks and crevices that are easy to overlook, thereby evading humans and their eradication efforts. Conversely, the seasoned pest controller is alert for cracks and crevices where it is likely to be profitable to place baits or spray surfaces.
To be effective, control measures must be comprehensive, sustained, and systematic; survival of just a few eggs is quite enough to regenerate a nearly exterminated pest population within a few generations, and recolonization from surrounding populations often is very rapid, too.

Another problem in controlling German cockroaches is the nature of their population behavior. Though they are not social and practice no organized maternal care, females carry oothecae of 18-50 eggs (average about 32) during incubation until just before hatching, instead of dropping them as most other species of cockroaches do. This protects the eggs from certain classes of predation. Then, after hatching, nymphs largely survive by consuming excretions and molts from adults, thereby establishing their own internal microbial populations and avoiding contact with most insecticidal surface treatments and baits. One effective control is insect growth regulators (
hydroprene,
methoprene
Methoprene is a juvenile hormone (JH) analog and insect growth regulator (IGR) used widely in pest control. Classified under Insecticide Resistance Action Committee (IRAC) group 7A, methoprene is an amber-colored liquid with a faint fruity odor. ...
, etc.), which act by preventing molting, thus prevent maturation of the various instars. Caulking baseboards and around pipes may prevent the travel of adults from one apartment to another within a building.
As an
adaptive consequence of pest control by poisoned glucose baits, a strain of German cockroaches has emerged that reacts to glucose as distastefully bitter. They refuse to eat baits sweetened with glucose, which presents an obstacle to their control, given that several common baits use glucose.
summary at BBC News
Comparison of three common cockroaches
Genome
The genome of the German cockroach was published in February 2018 in ''
Nature Ecology and Evolution
''Nature Ecology and Evolution'' is an online-only monthly peer-reviewed scientific journal published by Nature Portfolio covering all aspects of research on ecology and evolutionary biology. It was established in 2017. Its first editor-in-chief w ...
''.
The relatively large genome (2.0 Gb) harbours a very high number of proteins, of which most notably one group of
chemoreceptors
A chemoreceptor, also known as chemosensor, is a specialized sensory receptor which transduces a chemical substance ( endogenous or induced) to generate a biological signal. This signal may be in the form of an action potential, if the chemorece ...
, called the
ionotropic receptors
Ligand-gated ion channels (LICs, LGIC), also commonly referred to as ionotropic receptors, are a group of transmembrane ion-channel proteins which open to allow ions such as Na+, K+, Ca2+, and/or Cl− to pass through the membrane in res ...
, is particularly numerous. These chemoreceptors possibly allow the German cockroach to detect a broad range of chemical cues from toxins, food, pathogens, and pheromones.
See also
*
Blattellaquinone, a sex pheromone of the German cockroach
Notes
References
External links
German cockroachon the
UF /
IFAS Featured Creatures Web site
German cockroach fact sheetfrom the
Penn State #Redirect Pennsylvania State University
The Pennsylvania State University (Penn State or PSU) is a Public university, public Commonwealth System of Higher Education, state-related Land-grant university, land-grant research university with ca ...
Extension
{{DEFAULTSORT:German cockroach
Cockroaches
Household pest insects
Insects described in 1767
Taxa named by Carl Linnaeus