63-671: 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 feed on humans, although other species may parasitize humans opportunistically. Species that primarily parasitize bats are known as bat bugs . The insects are 3 to 9 millimetres (0.12 to 0.35 in) long and have flattened reddish-brown bodies with small nonfunctional wings. Adult Cimex are light brown to reddish-brown, flat and oval. The mouthparts are beak-like, and adapted for piercing and sucking. Following
126-411: A reproductive tract that functions during oviposition , but the male does not use this tract for sperm insemination . Instead, the male pierces the female's abdomen with his hypodermic 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 , a secondary genital structure that reduces
189-552: 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 45 °C (113 °F); all stages of life are killed by 7 minutes of exposure to 46 °C (115 °F). 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. Household insecticides often do not have
252-590: 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 , small cockroaches , 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 kairomones to communicate regarding nesting locations, feeding, and reproduction. The lifespan of Cimex varies by species and
315-463: A blood meal the abdomen is plump and darker in colour. The front wings are vestigial and reduced to pad-like structures. Cimex lacks hind wings. They have segmented abdomens with microscopic hairs that give them a banded appearance. Adults grow to 3 to 9 mm (0.12 to 0.35 in) long. The different species are very similar in morphology and can only be separated by microscopic examination. Sexual dimorphism occurs in C. lectularius , with
378-501: A cimicid has fed, causing it to move out of a danger zone after feeding. Most cimicids feed once every three to seven days in natural conditions. C. lectularius normally feeds once every seven days and Ornithocoris toledoi every eight days, though C. hemipterus has been observed feeding every day for several days (in hot climates). Excessively hot or cold temperatures disrupt normal behavior. All cimicids harbour bacterial symbionts in paired structures known as "mycetomes". Although
441-425: A convenient mammal to exploit as they roost communally, returning to the same roost regularly. It is perhaps to avoid the parasites that some species of bat regularly change roosts. The subfamily Haematosiphoninae use birds in the swift and swallow families, Apodidae and Hirundinidae . One species, P. cavernis , has a very limited distribution and appears to make use of only one species of host. Host switching
504-403: A final sexually mature adult stage. They shed their skins through ecdysis at each stage, discarding their outer exoskeleton, which is a somewhat clear, empty exoskeleton 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 . Each of the immature stages lasts about a week, depending on temperature and
567-612: A host species can vary between populations of a given species; the causes for this are unclear. The effects of cimicid feeding on the host include causing an immune response that results in discomfort, the transmission of pathogens, secondary infections at the wound site, physiological changes such as iron deficiency, and reduced fitness (slow growth, small size, or lack of reproductive success). Hosts can defend themselves against attack by choosing non-infected sites and by grooming, while cimicids can maximise their success by reducing feeding time, selecting feeding sites which are out of reach of
630-630: 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. 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
693-631: A human, which provided an abundant food supply that led to the growth and expansion of the ectoparasite populations. Cimicids are relatively specialized in their choice of hosts, compared to other bloodsucking insects. Most cimicids have a preferred host, but accept some others when presented with the choice, such as C. lectularius and C. hemipterus , which are most often found among humans, but can also survive by feeding on birds, bats, rabbits, and mice. The subfamilies Primicimicinae and Latrocimicinae use New World bats as their hosts, while Afrocimicinae and Cacodminae use Old World bats. Bats represent
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#1732868818416756-511: A laboratory attempt to crossbreed a female C. lectularius with C. hemipterus males, one nymph hatched out of 479 eggs laid. It possessed features of both species, suggesting it was a hybrid instead of a product of parthenogenesis . Cimicids are attracted to hosts by a variety of cues, including heat (even a temperature difference of 1 °C) and kairomones . Host cues (at least in some species, including C. lectularius and Stricticimex antennatus ) change from attractants to repellants after
819-567: 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
882-412: A moult or, if an adult, has thoroughly digested the meal. 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
945-486: A new mate. The males excrete an aggregation pheromone into the air that attracts virgin females and arrests other males. Cimicidae Subfamily Afrociminae Subfamily Cimicinae Subfamily Cacodminae Subfamily Haematosiphoninae Subfamily Latrocimicinae Subfamily Primicimicinae 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
1008-521: A prolonged effect on the bug population. Professional pest control experts may use potentially harmful substances such as chlorpyrifos . Cimex are obligatory hematophagous (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
1071-455: A single survivor of eradication, can be responsible for an entire infestation over a matter of weeks, rapidly producing generations of offspring. 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
1134-430: A steady temperature and opportunities for regular blood meals. However, the bats frequently groom themselves and each other, putting the parasites at risk of being eaten. Cimicids lessen this risk by hiding in concealed locations between feeding bouts, and by producing a repellent substance which makes them distasteful. In evolutionary terms, most species of cimicid probably specialised on insectivorous bats or birds, with
1197-412: 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
1260-610: A year in some instances. Cimicids are typically small, oval, flattened, wingless insects. They are stimulated to appear from their hiding places by cues such as a slight rise in the temperature of their surroundings. Among the family's distinctive characteristics are traumatic insemination , in which the male fertilises the eggs by piercing the female's abdominal wall with his intromittent organ . They also have distinctive paired structures called mycetomes inside their bodies, in which they harbour bacterial symbionts : these may help them to obtain nutrients they cannot get from blood. Although
1323-609: Is also dependent on feeding. Research on C. lectularius shows that it can survive a wide range of temperatures and atmospheric compositions. Below 16 °C (61 °F), adults enter semi-hibernation and can survive longer; they can survive for at least five days at −10 °C (14 °F), but die after 15 minutes of exposure to −32 °C (−26 °F). Common commercial and residential freezers reach temperatures low enough to kill most life stages of bed bug, with 95% mortality after 3 days at −12 °C (10 °F). They show high desiccation tolerance , surviving low humidity and
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#17328688184161386-442: Is dependent on several factors, including overlap in host detection cues and ability to digest different kinds of blood. For example, the red blood cells of chickens are about 3 to 5 μm longer in diameter than those of humans, making human blood more suitable for the narrow food canal of C. lectularius . C. hemipterus may be able to vary the size of its food canal, allowing it greater flexibility in its choice of hosts. Preference for
1449-420: Is rarely transmitted from cimicids to bats, but it has not been observed replicating after such transmission. The viruses HIV and hepatitis B can persist in C. lectularius for two weeks, but with no viral replication. The possibility of these and most other viruses being transmitted from C. lectularius to humans is considered extremely remote. Polyctenidae and Cimicidae are considered to be sister taxa ,
1512-432: 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 . Bed bugs have five immature nymph life stages and
1575-417: 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
1638-469: The Cretaceous , for the evolution of the first Cimicidae. When bats appeared some 50 million years later, the parasites presumably switched hosts, feeding on bats and birds from then on. The group colonised humans as hosts on three occasions. The genus Cimex is seen to be polyphyletic . An independent molecular analysis came to a similar conclusion, that bedbugs diversified and fed on other hosts long before
1701-519: The 57th annual meeting of the Entomological Society of America in 2009, newer generations of pesticide-resistant C. lectularius in Virginia were reported to survive only two months without feeding. 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. Cimex pierces
1764-631: 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 . 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
1827-506: The analysis. Instar An instar ( / ˈ ɪ n s t ɑːr / , 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 grow or assume a new form. Differences between instars can often be seen in altered body proportions, colors, patterns, changes in
1890-425: The availability of food, and the complete lifecycle can be completed in as little as two months (rather long compared to other ectoparasites ). 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
1953-472: The bat's pelage with these. Cimicids are a specialised group of blood-sucking parasites that primarily feed on bats, birds and humans. They are thought to have evolved from predatory heteropteran ancestors, with about 60% of extant species using bats as their primary hosts. Bats are social mammals and many species congregate in communal roosts to give birth and rear their young. These roosts provide excellent conditions for their arthropod ectoparasites, with
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2016-435: The blood of their hosts. They are often considered to be ectoparasites because, although they move away from the host after feeding, they remain within the confines of their host's roost, nest or dwelling; however, under a different definition, they may be considered to be micropredatory bloodsuckers. Reproduction in cimicids involves traumatic insemination ; although the female has a normal genital tract for laying eggs,
2079-427: The cost difference between ejaculate-dose dependence and mating frequency dependence have not been explored. 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 . These two names are not descriptive, so other terminologies are used). On fertilization,
2142-496: The developmental rates of species and still have no impact on the number of larval instars. As examples, lower temperatures and lower humidity often slow the rate of development and that may have an effect on how many molts an insect will undergo – an example of this is seen in the lepidopteran tobacco budworm . On the other hand, temperature affects the development rates of a number of hymenopterans without affecting numbers of instars or larval morphology, as observed in
2205-461: The existence of bats, suggesting that "bats were colonized several times independently, unless the evolutionary origin of bats has been grossly underestimated." Primicimex Bucimex Leptocimex Cadocmus and allies Paracimex Oeciacus and part of " Cimex " (inc C. hemipterus and C. pipistrelli ) part of " Cimex " (inc C. lectularius ) Afrocimicinae , Haematosiphoninae , Latrocimicinae were not included in
2268-432: The face, neck, and arms of a sleeping person. Bed bugs have mouth parts that saw through the skin, and inject saliva with anticoagulants 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
2331-405: 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 . 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
2394-400: 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 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
2457-563: The females' genes in the gene pool. In organisms, sexual selection 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,
2520-459: The fore limbs of bats away from the roost, and this is likely to be the means by which the insects disperse. The cimicids have no special adaptations to enable them to travel in this way, however the only two members of the Primicimicinae subfamily, Bucimex chilensis and Primicimex cavernis have claws and an erect a row of peg-like spines on the tarsus , and have been observed clinging to
2583-570: The former family also being flightless and specialized to feed on the blood of bats. A fossil bedbug, Quasicimex eilapinastes , was identified in 2008 from Late Cretaceous Burmese amber , aged 99 million years ago (mya). Molecular analysis of five mitochondrial and nuclear genes shows that the Cimicidae, a group of over 100 species, form a clade . The Primicimicinae is sister to the clade containing all other extant species. The analysis, dated using fossils, gives an estimated date of 115 mya, in
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2646-430: 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
2709-406: The host and hiding while they digest the blood, which may take several days. This means that they specialise in vertebrate hosts that return regularly to particular sites to nest, roost or sleep. Birds and bats suit these specific requirements, as do humans now that they live in dwellings, and these are the main hosts used by the bugs. Most cimicids are able to go for long periods without feeding, over
2772-422: The hosts grooming activities, choosing to feed at times when the host is inactive, and removing themselves to a safer environment promptly when satiated. Although viruses and other pathogens can be acquired by cimicids, they rarely transmit them to their hosts. O. vicarius is a vector of several arboviruses , but is not killed by these viruses. Trypanosoma cruzi , the trypanosome that causes Chagas disease ,
2835-409: The insects may acquire viruses and other pathogens while feeding, these do not normally replicate inside the insect, and the infections are not transmitted to new hosts. All cimicids are small, oval-shaped, and flat in appearance, although their bodies bulge after feeding. They do not fly, but have small, non-functional wing pads. They have beak-like mouthparts with which they pierce the skin and suck
2898-539: The last inseminating male sires more offspring than his predecessors. Males will mount any recently-fed bug, regardless of sex, and start probing its abdomen in the region of the spermalege, thus receiving tactile, morphological and behavioral cues revealing the sex of the mounted bug. Females occasionally die from a ruptured gut after insemination; insemination via the female reproductive tract does not normally occur, except under restrictive laboratory conditions. The females' spermalege contain immune cells that seem to reduce
2961-629: The latter term properly refers to the most well-known member of the family, Cimex lectularius , the common bed bug and its tropical relation Cimex hemipterus . The family contains over 100 species. Cimicids appeared in the fossil record in the Cretaceous period. When bats evolved in the Eocene , Cimicids switched hosts and now feed mainly on bats or birds . Members of the group have colonised humans on three occasions. Cimicids usually feed on their host's blood every three to seven days, crawling away from
3024-411: The male never uses it (except in the species Primicimex cavernis ), instead piercing the female's abdominal wall with his intromittent organ and injecting sperm into the spermalege , a storage structure; the sperm then migrate through the female's paragenital system to reach the eggs. This practice may have evolved as males competed with each other to place their sperm closer and closer to the ovaries;
3087-419: 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
3150-403: 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
3213-407: The number of body segments or head width. After shedding their exoskeleton (moulting), the juvenile arthropods continue in their life cycle until they either pupate or moult again. The instar period of growth is fixed; however, in some insects, like the salvinia stem-borer moth , the number of instars depends on early larval nutrition. Some arthropods can continue to moult after sexual maturity, but
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#17328688184163276-419: The possibility of dispersal to other sites via their winged hosts. On returning to a roost, a bat may only be available to cimicids for a short time before it cools down and enters a state of torpor , with reduced blood flow. When the bats lived in close proximity to humans, in caves or in the roofs of their huts, a new opportunity arose; the cimicids could make use of the large size and homeothermic properties of
3339-460: The return of their migratory hosts. The five nymphal instars (stages) must each take a blood meal to develop to the next stage. An undisturbed bug may take 3–15 minutes to ingest a full meal depending on its life stage. They can survive long periods of time without feeding, reappearing from their hiding places when hosts again become available. Adult bedbugs have been reported to live three to twelve months in an untreated household situation. In
3402-419: The risk of infection from traumatic insemination. Feeding is required for egg production in females and probably for sperm production in males. Egg-laying behavior varies among species. C. lectularius stops laying fertile eggs about 35 to 50 days after the last insemination. The American cliff swallow bug, Oeciacus vicarius , hibernates after mating in autumn and begins laying in spring, to coincide with
3465-557: 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 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 . Female Cimex possess
3528-537: The significance of these has not been fully studied, they may be concerned with the biosynthesis of nutrients that the insect cannot synthesize itself, as is the case in other blood-sucking insects. Many cimicids can go without food for long periods, one and a half years in some instances. This allows them to survive the winter at summer bat roosts even when the bats are hibernating elsewhere, and may be an important adaptive trait because of their limited dispersal ability. Cimicids have occasionally been observed clinging to
3591-414: The skin of its host with a stylet fascicle, rostrum , or "beak". The rostrum is composed of the maxillae and mandibles , 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
3654-409: 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
3717-403: The species and the environmental conditions, as described for a number of species of Lepidoptera. However, it is believed that the number of instars can be physiologically constant per species in some insect orders, as for example Diptera and Hymenoptera . The number of larval instars is not directly related to speed of development. For instance, environmental conditions may dramatically affect
3780-450: 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. 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
3843-462: The stages between these subsequent moults are generally not called instars. For most insect species, an instar is the developmental stage of the larval forms of holometabolous (complete metamorphism) or nymphal forms of hemimetabolous (incomplete metamorphism) insects, but an instar can be any developmental stage including pupa or imago (the adult, which does not moult in insects). The number of instars an insect undergoes often depends on
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#17328688184163906-404: 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
3969-425: The wounding and immunological costs of traumatic insemination. Injected sperm travel via the haemolymph (blood) to sperm storage structures called seminal conceptacles, with fertilisation eventually taking place at the ovaries . The " Cimex alarm pheromone" consists of ( E )-2- octenal and ( E )-2- hexenal . It is released when the insect is disturbed, as during an attack by a predator. A 2009 study demonstrated
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