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 feed on humans, although other species may parasitize humans opportunistically. Species that primarily parasitize bats are known as bat bugs.

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 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 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, 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 is also dependent on feeding.

Taxonomy

* '' Cimex adjunctus'', bat bug found in Eastern United States
* ''Cimex antennatus'', bat bug from Pacific North America
* '' Cimex brevis''
* ''Cimex columbarius'', infesting pigeon nests
* ''Cimex emarginatus'', bat bug from the Balkan Peninsula
* ''Cimex incrassatus'',
* ''Cimex japonicus'', bat bug found in Japan
* ''Cimex latipennis'', bat bug from Pacific North America
* '' Cimex lectularius'', common bed bug with cosmopolitan distribution
* '' Cimex hemipterus'', tropical bed bug
* ''Cimex pilosellus'', bat bug found in northern United States and Canada
* ''Cimex pipistrelli'', 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.

Feeding habits

''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 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 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 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, 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 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 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.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 that functions during oviposition