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''Cimex'' is a genus of insects in the family
Cimicidae The Cimicidae are a family of small parasitic bugs that feed exclusively on the blood of warm-blooded animals. They are called cimicids or, loosely, bed bugs, though the latter term properly refers to the most famous member of the family, '' ...
. ''Cimex'' species are
ectoparasite Parasitism is a close relationship between species, where one organism, the parasite, lives on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The entomologist E. O. Wilson has ...
s that typically feed on the blood of birds and mammals. Two species, '' Cimex lectularius'' and ''
Cimex hemipterus ''Cimex hemipterus'', known as the tropical bed bug, is a species of bed bugs within the ''Cimicidae'' family that primarily resides in tropical climates. However, it has been reported that this species can live in more temperate climates along w ...
'', are known as bed bugs and frequently feed on humans, although other species may parasitize humans opportunistically. Species that primarily parasitize bats are known as
bat bug Bat bugs are blood-sucking insect parasites that feed primarily on the blood of bats. The name has been applied to members of the family ''Cimicidae'' (e.g. ''Cimex lectularius'', '' Afrocimex constrictus'') and also to members of the family '' ...
s. The insects are long and have flattened reddish-brown bodies with small nonfunctional wings.


Description

Adult ''Cimex'' are light brown to reddish-brown, flat and oval. The mouthparts are beak-like, and adapted for piercing and sucking. Following a blood meal the abdomen is plump and darker in colour. The front wings are vestigial and reduced to pad-like structures and there are no hind wings. ''Cimex'' have segmented abdomens with microscopic hairs that give them a banded appearance. Adults grow to long. The different species are very similar in
morphology Morphology, from the Greek and meaning "study of shape", may refer to: Disciplines *Morphology (archaeology), study of the shapes or forms of artifacts *Morphology (astronomy), study of the shape of astronomical objects such as nebulae, galaxies, ...
and can only be separated by microscopic examination. Sexual dimorphism occurs in ''C. lectularius'', with the females larger in size than the males on average. The abdomens of the sexes differ in that the males appear to have "pointed" abdomens, which are actually their copulatory organs, while females have more rounded abdomens. Newly hatched
nymphs A nymph ( grc, νύμφη, nýmphē, el, script=Latn, nímfi, label=Modern Greek; , ) in ancient Greek folklore is a minor female nature deity. Different from Greek goddesses, nymphs are generally regarded as personifications of nature, are typ ...
are translucent, light in color at first, becoming browner as they moult and approach maturity. A ''Cimex'' nymph of any age that has just consumed a blood meal has a bright red, translucent abdomen, fading to brown over the next several hours, and to opaque black within two days as the insect digests its meal. ''Cimex'' may be mistaken for other insects, such as
booklice Psocoptera are a paraphyletic group of insects that are commonly known as booklice, barklice or barkflies. The name Psocoptera has been replaced with Psocodea in recent literature, with the inclusion of the former order Phthiraptera into Psocode ...
, small
cockroach Cockroaches (or roaches) are a paraphyletic group of insects belonging to Blattodea, containing all members of the group except termites. About 30 cockroach species out of 4,600 are associated with human habitats. Some species are well-known as ...
es, or carpet beetles; however, when warm and active, their movements are more ant-like, and like most other true bugs, they emit a characteristic disagreeable odor when crushed. ''Cimex'' use pheromones and
kairomone A kairomone (a coinage using the Greek καιρός ''opportune moment'', paralleling pheromone"kairomone, n.". OED Online. September 2012. Oxford University Press. http://www.oed.com/view/Entry/241005?redirectedFrom=kairomone (accessed 3 Octob ...
s to communicate regarding nesting locations, feeding, and reproduction. The lifespan of ''Cimex'' varies by species and is also dependent on feeding.


Taxonomy

* ''
Cimex adjunctus ''Cimex'' is a genus of insects in the family Cimicidae. ''Cimex'' species are ectoparasites that typically feed on the blood of birds and mammals. Two species, ''Cimex lectularius'' and ''Cimex hemipterus'', are known as bed bugs and frequently ...
'', bat bug found in Eastern United States * ''
Cimex antennatus ''Cimex antennatus'' is a species of Cimicidae (bed bugs) endemic to North America. Its primary hosts are bat Bats are mammals of the order Chiroptera.''cheir'', "hand" and πτερόν''pteron'', "wing". With their forelimbs adapted as ...
'', bat bug from Pacific North America * ''
Cimex brevis ''Cimex'' is a genus of insects in the family Cimicidae. ''Cimex'' species are ectoparasites that typically feed on the blood of birds and mammals. Two species, ''Cimex lectularius'' and ''Cimex hemipterus'', are known as bed bugs and frequently ...
'' * ''
Cimex columbarius ''Cimex'' is a genus of insects in the family Cimicidae. ''Cimex'' species are ectoparasites that typically feed on the blood of birds and mammals. Two species, ''Cimex lectularius'' and ''Cimex hemipterus'', are known as bed bugs and frequently ...
'', infesting pigeon nests * ''
Cimex emarginatus ''Cimex'' is a genus of insects in the family Cimicidae. ''Cimex'' species are ectoparasites that typically feed on the blood of birds and mammals. Two species, ''Cimex lectularius'' and ''Cimex hemipterus'', are known as bed bugs and frequently ...
'', bat bug from the
Balkan Peninsula The Balkans ( ), also known as the Balkan Peninsula, is a geographical area in southeastern Europe with various geographical and historical definitions. The region takes its name from the Balkan Mountains that stretch throughout the whol ...
* ''
Cimex incrassatus ''Cimex'' is a genus of insects in the family Cimicidae. ''Cimex'' species are ectoparasites that typically feed on the blood of birds and mammals. Two species, ''Cimex lectularius'' and ''Cimex hemipterus'', are known as bed bugs and frequently ...
'', * ''
Cimex japonicus ''Cimex'' is a genus of insects in the family Cimicidae. ''Cimex'' species are ectoparasites that typically feed on the blood of birds and mammals. Two species, ''Cimex lectularius'' and ''Cimex hemipterus'', are known as bed bugs and frequently ...
'', bat bug found in Japan * ''
Cimex latipennis ''Cimex'' is a genus of insects in the family Cimicidae. ''Cimex'' species are ectoparasites that typically feed on the blood of birds and mammals. Two species, ''Cimex lectularius'' and ''Cimex hemipterus'', are known as bed bugs and frequently ...
'', bat bug from Pacific North America * '' Cimex lectularius'', common bed bug with cosmopolitan distribution * ''
Cimex hemipterus ''Cimex hemipterus'', known as the tropical bed bug, is a species of bed bugs within the ''Cimicidae'' family that primarily resides in tropical climates. However, it has been reported that this species can live in more temperate climates along w ...
'', tropical bed bug * '' Cimex pilosellus'', bat bug found in northern United States and Canada * ''
Cimex pipistrelli ''Cimex'' is a genus of insects in the family Cimicidae. ''Cimex'' species are ectoparasites that typically feed on the blood of birds and mammals. Two species, ''Cimex lectularius'' and ''Cimex hemipterus'', are known as bed bugs and frequently ...
'', European bat bug


Biology

Research on ''C. lectularius'' shows that it can survive a wide range of temperatures and atmospheric compositions. Below , adults enter semihibernation and can survive longer; they can survive for at least five days at , but die after 15 minutes of exposure to . Common commercial and residential freezers reach temperatures low enough to kill most life stages of bed bug, with 95% mortality after 3 days at . They show high desiccation tolerance, surviving low humidity and a 35–40 °C range even with loss of one-third of body weight; earlier life stages are more susceptible to drying out than later ones. The thermal death point for ''C. lectularius'' is ; all stages of life are killed by 7 minutes of exposure to . Bed bugs apparently cannot survive high concentrations of carbon dioxide for very long; exposure to nearly pure nitrogen atmospheres, however, appears to have relatively little effect even after 72 hours. (abstracted from a poster presentation in Prague, 19–22 Jul) Household insecticides often do not have a prolonged effect on the bug population. Professional pest control experts may use potentially harmful substances such as
chlorpyrifos Chlorpyrifos (CPS), also known as Chlorpyrifos ethyl, is an organophosphate pesticide that has been used on crops, animals, and buildings, and in other settings, to kill several pests, including insects and worms. It acts on the nervous systems ...
.


Feeding habits

''Cimex'' are obligatory
hematophagous Hematophagy (sometimes spelled haematophagy or hematophagia) is the practice by certain animals of feeding on blood (from the Greek words αἷμα ' "blood" and φαγεῖν ' "to eat"). Since blood is a fluid tissue rich in nutritious pr ...
(bloodsucking) insects. Most species feed on humans only when other prey are unavailable. They obtain all the additional moisture they need from water vapor in the surrounding air. ''Cimex'' are attracted to their hosts primarily by carbon dioxide, secondarily by warmth, and also by certain chemicals. Bed bugs prefer exposed skin, preferably the face, neck, and arms of a sleeping person. Bed bugs have mouth parts that saw through the skin, and inject saliva with
anticoagulant Anticoagulants, commonly known as blood thinners, are chemical substances that prevent or reduce coagulation of blood, prolonging the clotting time. Some of them occur naturally in blood-eating animals such as leeches and mosquitoes, where the ...
s and painkillers. Sensitivity of humans varies from extreme allergic reaction to no reaction at all (about 20%). The bite usually produces a swelling with no red spot, but when many bugs feed on a small area, reddish spots may appear after the swelling subsides. The bite marks may appear in a straight line. Although under certain cool conditions adult ''Cimex'' can live for over a year without feeding, under typically warm conditions they try to feed at five- to ten-day intervals, and adults can survive for about five months without food. Younger instars cannot survive nearly as long, though even the vulnerable newly hatched first instars can survive for weeks without taking a blood meal. At the 57th annual meeting of the
Entomological Society of America The Entomological Society of America (ESA) was founded in 1889 and today has more than 7,000 members, including educators, extension personnel, consultants, students, researchers, and scientists from agricultural departments, health agencies, ...
in 2009, newer generations of pesticide-resistant ''C. lectularius'' in Virginia were reported to survive only two months without feeding. citing DNA from human blood meals can be recovered from ''Cimex'' for up to 90 days, which means they can be used for forensic purposes in identifying on whom the bed bugs have fed.


Feeding physiology

''Cimex'' pierces the skin of its host with a stylet fascicle,
rostrum Rostrum may refer to: * Any kind of a platform for a speaker: **dais **pulpit * Rostrum (anatomy), a beak, or anatomical structure resembling a beak, as in the mouthparts of many sucking insects * Rostrum (ship), a form of bow on naval ships * R ...
, or "beak". The rostrum is composed of the maxillae and
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 teeth in place. The mandible sits beneath the maxilla. It is the only movable bone ...
, which have been modified into elongated shapes from a basic, ancestral style. The right and left maxillary stylets are connected at their midline and a section at the centerline forms a large food canal and a smaller salivary canal. The entire maxillary and mandibular bundle penetrates the skin. The tips of the right and left maxillary stylets are not the same; the right is hook-like and curved, and the left is straight. The right and left mandibular stylets extend along the outer sides of their respective maxillary stylets and do not reach anywhere near the tip of the fused maxillary stylets. The stylets are retained in a groove in the labium, and during feeding, they are freed from the groove as the jointed labium is bent or folded out of the way; its tip never enters the wound. The mandibular stylet tips have small teeth, and through alternately moving these stylets back and forth, the insect cuts a path through tissue for the maxillary bundle to reach an appropriately sized blood vessel. Pressure from the blood vessel itself fills the insect with blood in three to five minutes. The bug then withdraws the stylet bundle from the feeding position and retracts it back into the labial groove, folds the entire unit back under the head, and returns to its hiding place. It takes between five and ten minutes for a ''Cimex'' to become completely engorged with blood. In all, the insect may spend less than 20 minutes in physical contact with its host, and does not try to feed again until it has either completed a moult or, if an adult, has thoroughly digested the meal.


Reproduction

Since males are attracted to large body size, any ''Cimex'' with a recent blood meal can be seen as a potential mate. However, males will mount unfed, flat females on occasion. The female is able to curl her abdomen forward and underneath toward the head to deter the male if she does not wish to mate. Males are generally unable to discriminate between the sexes until after mounting, but can do so before insemination. North Carolina State University found that bed bugs in contrast to most other insects tolerate incest and are able to genetically withstand the effects of
inbreeding Inbreeding is the production of offspring from the mating or breeding of individuals or organisms that are closely related genetically. By analogy, the term is used in human reproduction, but more commonly refers to the genetic disorders and ...
quite well. Male bed bugs sometimes attempt to mate with other males and pierce their abdomens. This behaviour occurs because sexual attraction in bed bugs is based primarily on size, and males mount any freshly fed partner regardless of sex. All ''Cimex'' mate by
traumatic insemination Traumatic insemination, also known as hypodermic insemination, is the mating practice in some species of invertebrates in which the male pierces the female's abdomen with his aedeagus and injects his sperm through the wound into her abdominal c ...
.Carayon, J. 1959 Insémination par "spermalège" et cordon conducteur de spermatozoids chez Stricticimex brevispinosus Usinger (Heteroptera, Cimicidae). Rev. Zool. Bot. Afr. 60, 81–104. Female ''Cimex'' possess a
reproductive tract The reproductive system of an organism, also known as the genital system, is the biological system made up of all the anatomical organs involved in sexual reproduction. Many non-living substances such as fluids, hormones, and pheromones are al ...
that functions during oviposition, but the male does not use this tract for sperm insemination. Instead, the male pierces the female's
abdomen The abdomen (colloquially called the belly, tummy, midriff, tucky or stomach) is the part of the body between the thorax (chest) and pelvis, in humans and in other vertebrates. The abdomen is the front part of the abdominal segment of the torso. ...
with his
hypodermic A hypodermic needle (from Greek ὑπο- (''hypo-'' = under), and δέρμα (''derma'' = skin)), one of a category of medical tools which enter the skin, called sharps, is a very thin, hollow tube with one sharp tip. It is commonly used w ...
penis and ejaculates into the body cavity. In all bed bug species except ''Primicimex cavernis,'' sperm are injected into the mesospermalege, a component of the
spermalege The spermalege (also known as the organ of BerleseSiva-Jothy, M. T. (2006) "Trauma, disease and collateral damage: conflict in cimicids," ''Philosophical Transactions of the Royal Society B,'' 361, 269–275.) is a special-purpose organ found in fe ...
, a secondary genital structure that reduces the wounding and immunological costs of traumatic insemination. Injected sperm travel via the haemolymph (blood) to
sperm storage Female sperm storage is a biological process and often a type of sexual selection in which sperm cells transferred to a female during mating are temporarily retained within a specific part of the reproductive tract before the oocyte, or egg, is fe ...
structures called seminal conceptacles, with fertilisation eventually taking place at the
ovaries The ovary is an organ in the female reproductive system that produces an ovum. When released, this travels down the fallopian tube into the uterus, where it may become fertilized by a sperm. There is an ovary () found on each side of the body. T ...
. The "''Cimex'' alarm pheromone" consists of (''E'')-2- octenal and (''E'')-2-
hexenal ''cis''-3-Hexenal, also known as (''Z'')-3-hexenal and leaf aldehyde, is an organic compound with the formula CH3CH2CH=CHCH2CHO. It is classified as an unsaturated aldehyde. It is a colorless liquid and an aroma compound with an intense odor of ...
. It is released when the insect is disturbed, as during an attack by a predator. A 2009 study demonstrated the alarm pheromone is also released by male ''Cimex'' to repel other males that attempt to mate with them. ''C. lectularius'' and ''C. hemipterus'' mate with each other given the opportunity, but the eggs then produced are usually sterile. In a 1988 study, one of 479 eggs was fertile and resulted in a hybrid, ''Cimex hemipterus'' × ''lectularius''.


Sperm protection

''Cimex lectularius'' males have environmental microbes on their genitals. These microbes damage sperm cells, leaving them unable to fertilize female gametes. Due to these dangerous microbes, males have evolved antimicrobial ejaculate substances that prevent sperm damage. When the microbes contact sperm or the male genitals, the bed bug releases antimicrobial substances. Many species of these microbes live in the bodies of females after mating. The microbes can cause infections in the females. It has been suggested that females receive benefit from the ejaculate. Although the benefit is not direct, females are able to produce more eggs than optimum increasing the amount of the females' genes in the gene pool.


Sperm and seminal fluid allocation

In organisms,
sexual selection Sexual selection is a mode of natural selection in which members of one biological sex choose mates of the other sex to mate with (intersexual selection), and compete with members of the same sex for access to members of the opposite sex (int ...
extends past differential reproduction to affect sperm composition, sperm competition, and ejaculate size. Males of ''C. lectularius'' allocate 12% of their sperm and 19% of their seminal fluid per mating. Due to these findings, Reinhard et al. proposed that multiple mating is limited by seminal fluid and not sperm. After measuring ejaculate volume, mating rate and estimating sperm density, Reinhardt et al. showed that mating could be limited by seminal fluid. Despite these advances, the cost difference between ejaculate-dose dependence and mating frequency dependence have not been explored.


Egg production

Males fertilize females only by traumatic insemination into the structure called the ectospermalege (the organ of Berlese, however the organ of Ribaga, as it was first named, was first designated as an organ of
stridulation Stridulation is the act of producing sound by rubbing together certain body parts. This behavior is mostly associated with insects, but other animals are known to do this as well, such as a number of species of fish, snakes and spiders. The mech ...
. These two names are not descriptive, so other terminologies are used). On fertilization, the female's ovaries finish developing, which suggests that sperm plays a role other than fertilizing the egg. Fertilization also allows for egg production through the
corpus allatum In insect physiology and anatomy, the corpus allatum (plural: corpora allata) is an endocrine gland that generates juvenile hormone; as such, it plays a crucial role in metamorphosis. Surgical removal of the corpora allata (an allatectomy) can cau ...
. Sperm remains viable in a female's spermathecae (a better term is conceptacle), a sperm-carrying sack, for a long period of time as long as body temperature is optimum. The female lays fertilized eggs until she depletes the sperm found in her conceptacle. After the depletion of sperm, she lays a few sterile eggs. The number of eggs a ''C. lectularius'' female produces does not depend on the sperm she harbors, but on the female's nutritional level.


Alarm pheromones

In ''C. lectularius'', males sometimes mount other males because male sexual interest is directed at any recently fed individual regardless of their sex, but unfed females may also be mounted. Traumatic insemination is the only way for copulation to occur in ''Cimex''. Females have evolved the spermalege to protect themselves from wounding and infection. Because males lack this organ, traumatic insemination could leave them badly injured. For this reason, males have evolved alarm pheromones to signal their sex to other males. If a male ''C. lectularius'' mounts another male, the mounted male releases the pheromone signal and the male on top stops before insemination. Females are capable of producing alarm pheromones to avoid multiple mating, but they generally do not do so. Two reasons are proposed as to why females do not release alarm pheromones to protect themselves. First, alarm pheromone production is costly. Due to egg production, females may refrain from spending additional energy on alarm pheromones. The second proposed reason is that releasing the alarm pheromone reduces the benefits associated with multiple mating. Benefits of multiple mating include material benefits, better quality nourishment or more nourishment, genetic benefits including increased fitness of offspring, and finally, the cost of resistance may be higher than the benefit of consent—which appears the case in ''C. lectularius''.


Life stages

Bed bugs have five immature nymph life stages and a final sexually mature adult stage. They shed their skins through ecdysis at each stage, discarding their outer exoskeleton, which is somewhat clear, empty exoskeletons of the bugs themselves. ''Cimex'' must molt six times before becoming fertile adults, and must consume at least one blood meal to complete each
molt In biology, moulting (British English), or molting (American English), also known as sloughing, shedding, or in many invertebrates, ecdysis, is the manner in which an animal routinely casts off a part of its body (often, but not always, an outer ...
. Each of the immature stages lasts about a week, depending on temperature and the availability of food, and the complete lifecycle can be completed in as little as two months (rather long compared to other
ectoparasites Parasitism is a close relationship between species, where one organism, the parasite, lives on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The entomologist E. O. Wilson has c ...
). Fertilized females with enough food lay three to four eggs each day continually until the end of their lifespans (about nine months under warm conditions), possibly generating as many as 500 eggs in this time. Genetic analysis has shown that a single pregnant ''Cimex'', possibly a single survivor of eradication, can be responsible for an entire infestation over a matter of weeks, rapidly producing generations of offspring. File:Cimex lectularius 3.jpg , Slide of ''C. lectularius'' File:bedbug1.JPG , On the right is recently sloughed skin from its nymph stage File:Bed bug nymph, Cimex lectularius.jpg , Nymph feeding on host File:Cimex lectularius2.jpg , Blood-fed stage (note differences in color with respect to digestion of blood meal)


Host searching

''Cimex lectularius'' only feeds every five to seven days, which suggests that it does not spend the majority of its life searching for a host. When a ''Cimex'' is starved, it leaves its shelter and searches for a host. If it successfully feeds, it returns to its shelter; otherwise, it continues to search for a host. After searching—regardless of whether or not it has eaten—the ''Cimex'' returns to the shelter to aggregate before the photophase (period of light during a day-night cycle). Reis argues that two reasons explain why ''C. lectularius'' would return to its shelter and aggregate after feeding. One is to find a mate and the other is to find shelter to avoid getting smashed after eating.


Aggregation and dispersal behavior

''Cimex lectularius'' aggregates under all life stages and mating conditions. ''Cimex'' may choose to aggregate because of predation, resistance to desiccation, and more opportunities to find a mate. Airborne pheromones are responsible for aggregations. Another source of aggregation could be the recognition of other ''C. lectularius'' bugs through mechanoreceptors located on their antennae. Aggregations are formed and disbanded based on the associated cost and benefits. Females are more often found separate from the aggregation than males. Females are more likely to expand the population range and find new sites. Active female dispersal can account for treatment failures. Males, when found in areas with few females, abandon an aggregation to find a new mate. The males excrete an aggregation pheromone into the air that attracts virgin females and arrests other males.


References

{{Taxonbar , from=Q10452938 Bed bug Cimicidae Cimicomorpha genera