Bed bugs are parasitic insects of the cimicid family that feed exclusively on blood. The term most commonly refers to members of the genus Cimex of which Cimex lectularius, the common bed bug, is the best known as it prefers to feed on human blood although other Cimex species are specialized to other animals, e.g., bat bugs, C. pipistrelli (Europe), C. pilosellus (western US), and C. adjunctus (entire eastern US).
The name of the "bed bug" is derived from the preferred habitat of Cimex lectularius: warm houses and especially nearby or inside of beds and bedding or other sleep areas. Bed bugs are mainly active at night, but are not exclusively nocturnal. They usually feed on their hosts without being noticed.
A number of adverse health effects may result from bed bug bites, including skin rashes, psychological effects, and allergic symptoms. Diagnosis involves both finding bed bugs and the occurrence of compatible symptoms.
Bed bugs have been known as human parasites for thousands of years. At a point in the early 1940s, they were mostly eradicated in the developed world, but have increased in prevalence since 1995. Because infestation of human habitats has been on the increase, bed bug bites and related conditions have been on the rise as well.
Main article: Bed bug infestation
Bed bugs can cause a number of health effects, including skin rashes, psychological effects, and allergic symptoms. They are able to be infected by at least 28 human pathogens, but no study has clearly found that the insect is able to transmit the pathogen to a human being. Bed bug bites or cimicosis may lead to a range of skin manifestations from no visible effects to prominent blisters.
Diagnosis involves both finding bed bugs and the occurrence of compatible symptoms.Treatment involves the elimination of the insect and measure to help with the symptoms until they resolve. They have been found with methicillin-resistant Staphylococcus aureus(MRSA) and with vancomycin-resistant Enterococcus faecium (VRE), but the significance of this is still unknown.
Dwellings can become infested with bed bugs in a variety of ways, such as:
- Bugs and eggs inadvertently brought in from other infested dwellings by visiting pets; or a visiting person's clothing or luggage;
- Infested items (such as furniture, clothing, or backpacks) brought in;
- Nearby dwellings or infested items, if easy routes are available for travel (through duct work or false ceilings);
- Wild animals (such as bats or birds) that may also harbour bed bugs or related species such as the bat bug;
- People or pets visiting an infested area (apartment, subway, movie theatre, or hotel) and carrying the bugs to another area on their clothing, luggage, or bodies.
Bed bug eggs and two adult bed bugs from inside a dresser.
Bed bugs are elusive and usually nocturnal (peak activity usually occurs between 10:00 p.m. - 6:00 a.m.), which can make their detection difficult. They often lodge in dark crevices, and the tiny adhesive eggs can be nestled by the hundreds in fabric seams. Aside from bite symptoms, signs include fecal spots (small dark sand-like droppings that occur in patches around and especially beneath nests), blood smears on sheets (fecal spots that are re-wetted will smear like fresh blood), and the presence of their empty molted exoskeletons.
Although bed bugs can be found singly, they tend to congregate once established. Although they are strictly parasitic, they spend only a tiny fraction of their life cycles physically attached to their hosts. Once feeding is complete, a bed bug will relocate to a place close to a known host, commonly in or near beds or couches in clusters of adults, juveniles, and eggs which entomologists call harborage areas or simply harborages to which the insect will return after future feedings by following chemical trails. These places can vary greatly in format, including luggage, inside of vehicles, within furniture, amongst bedside clutter, even inside electrical sockets and nearby laptop computers. Bed bugs may also nest near animals that have nested within a dwelling, such as bats, birds, or rodents. They are also capable of surviving on domestic cats and dogs, though humans are the preferred host of Cimex lectularius.
A bed bug detection dog in New York.
Bed bugs can also be detected by their characteristic smell of rotting raspberries. Bed bug detection dogs are trained to pinpoint infestations, with a possible accuracy rate of 97.5%, based upon tests conducted under controlled conditions by researchers. The success rates in these tests may not reflect real-world success rates of pest companies' dogs, operating with many more variables in the field.
Dog detection can often occur in minutes where a pest control practitioner might need an hour. In the United States, about 100 dogs are used to find bed bugs as of mid-2009. A few companies are experimenting with high speed gas chromatography to detect bed bugs.
Eradication of bed bugs frequently requires a combination of pesticide and nonpesticide approaches. Pesticides that have historically been found to be effective include: pyrethroids, dichlorvos and malathion. Resistance to pesticides has increased significantly over time and negative health effects from their use are of concern.
Mechanical approaches, such as vacuuming up the insects and heat treating or wrapping mattresses, have been recommended. A combination of heat and drying treatments have been found to be most effective. For public health reasons, individuals are encouraged to call a professional pest control service to eradicate bed bugs in a home, rather than attempting to do it themselves, particularly if they live in a multi-family building.
The carbamate insecticide propoxur is highly toxic to bed bugs, but in the United States, the Environmental Protection Agency (EPA)has been reluctant to approve such an indoor use because of its potential toxicity to children after chronic exposure.
Although occasionally applied as a safe indoor pesticide treatment for other insects, boric acid is ineffectual against bed bugs because bed bugs do not groom. The fungus Beauveria bassiana is being researched for its ability to control bed bugs.
Natural enemies of bed bugs include the masked hunter insect (also known as "masked bed bug hunter"),cockroaches, ants, spiders (particularly Thanatus flavidus), mites and centipedes (particularly the house centipede). Biological pest control is currently not considered practical for eliminating bed bugs from human dwellings.
Adult bed bugs are light brown to reddish-brown, flattened, oval-shaped and have no hind wings. The front wings are vestigial and reduced to pad-like structures. Bed bugs have segmented abdomens with microscopic hairs that give them a banded appearance. Adults grow to 4–5 mm in length and 1.5–3 mm wide.
Newly hatched nymphs are translucent, lighter in color and become browner as they moult and reach maturity. A bed bug of any age that has just consumed a blood meal will appear to have a bright red translucent abdomen; this color will fade to brown over the next several hours and within two days will become opaque and black as the insect digests its meal. Bed bugs 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.
Bed bugs use pheromones and kairomones to communicate regarding nesting locations, feeding and reproduction.
The life span of bed bugs varies by species and is also dependent on feeding.
Bed bugs can survive a wide range of temperatures and atmospheric compositions. Below 16.1 °C (61.0 °F), adults enter semihibernation and can survive longer; they can survive for at least five days at −10 °C (14 °F), but will die after 15 minutes of exposure to −32 °C (−26 °F). 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 high: 45 °C (113 °F), and 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
A Scanning electron micrograph (SEM) of Cimex lectularius, digitally colorized with the insect's skin-piercing mouthparts highlighted in purple and red.
Bed bugs 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. Bed bugs are attracted to their hosts primarily by carbon dioxide, secondarily by warmth, and also by certain chemicals. Bedbugs prefer exposed skin, preferably the face, neck and arms of a sleeping individual.
Although under certain cool conditions adult bed bugs can live for over a year without feeding under typically warm conditions they will 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 in 2009, newer generations of pesticide-resistant bed bugs in Virginia were reported to survive only two months without feeding.
DNA from human blood meals can be recovered from bed bugs for up to 90 days, which may allow them to be used for forensic purposes in identifying on whom the bed bugs have been feeding.
A bed bug pierces the skin of its host with what is called a stylet fascicle, rostrum, or "beak". This is a unit 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 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 bed bug to become completely engorged with blood. In all, the insect may have spent less than 20 minutes in physical contact with its host, and it will not attempt to feed again until it has either completed a molt or, if an adult, has thoroughly digested the meal.
A bed bug (Cimex lectularius)traumatically inseminates another
All bed bugs mate by traumatic insemination. Female bed bugs possess 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 genitalia 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 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.
Male bed bugs sometimes attempt to mate with other males and pierce the latter in the abdomen This behaviour occurs because sexual attraction in bed bugs is based primarily on size, and males will mount any freshly fed partner regardless of sex. The "bed bug alarm pheromone" consists of (E)-2-octenal and (E)-2-hexenal. It is released when a bed bug is disturbed, as during an attack by a predator. A 2009 study demonstrated the alarm pheromone is also released by male bed bugs to repel other males who attempt to mate with them.
C. lectularius and C. hemipterus will 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, C. hemipterus ×lectularius.
Bed bugs have six life stages (five immature nymph stages and a final sexually mature adult stage). They will shed their skins through ecdysis at each stage, discarding their outer shells which are clear, empty exoskeletons of the bugs themselves. Bed bugs must molt six times before becoming fertile adults and must take a blood meal in order to complete each molt.
Each of the immature stages lasts approximately a week, depending on temperature and the availability of food, and the complete life cycle can be completed in as little as two months (which is actually rather long compared to other ectoparasites). Fertilized females with enough food will lay three to four eggs each day continually until the end of their life spans (about nine months under warm conditions), possibly generating as many as 500 eggs in this time.