A parasite is an animal or plant that lives in or on another living animal or plant. The parasite obtains nourishment from the host without either benefiting or, at least in the short term, killing the host. An ectoparasite is just a parasite that lives primarily on the outer surface of its host.
The Bed Bug (scientific name Cimex lectularius) is one of several closely related species of parasitic bugs that feed on blood. All of these species are relatively host specific (that is, they feed from only one species of host), and the Bed Bug shows a strong preference for feeding on humans.
Bed Bugs are widely distributed, and have been found in association with man worldwide. They are believed to have evolved from a bug that preyed on cave dwelling bats or pigeons, and their association with man to be (relatively) recent.
The adult Bed Bug is brown, oval, flattened, and about 4-5 mm in length when unfed. Newly hatched nymphs are paler and somewhat translucent. After feeding the body becomes swollen and elongated, and the color becomes darker (a red or rusty brown). All stages are wingless.
The Bed Bugs life cycle is similar to that of cockroaches. Female Bed Bugs lay a single small, ovoid, milky white egg (under one mm in length) that has a cap at one end. The eggs are cemented to surfaces by the female (making them very difficult to dislodge by simple cleaning techniques). Females may lay up to five eggs per day, with a total production of about 500 during their lifetime. The eggs hatch after about ten days, with the nymph Bed Bug pushing open the cap.
Nymph Bed Bugs look like small versions of the adult, and progress through five molts before reaching the sexually mature adult stage. Development to adult takes about five weeks under average conditions. The nymphs require a blood meal prior to each molt, and the adult females require a blood meal in order to produce each batch of eggs.
Bed Bugs are nocturnal and cryptic, excellent survival characteristics for a parasite. They prefer to live in narrow cracks close to the hosts resting site (seeming to prefer horizontal cracks over vertical), and will rarely leave the protection of their harborage until the environment is both dark and quiet. They are gregarious, and like to be in contact with other Bed Bugs when resting.
Feeding usually takes place in the early hours of the morning when the host is immobile, with adults feeding on average about every three to five nights. They locate the host by using environmental clues such as warmth and respiratory signs, and exposed areas of the host are most likely to be selected as feeding sites. Feeding is usually completed within a few minutes.
Bed Bugs produce a sweet sickly odor from glands at their anal end as soon as they start to feed. This acts as a stimulant to other Bed Bugs, and causes them to increase their activity in search of food. Feeding causes considerable abdominal swelling of the insect in order to accommodate the blood. This increase in size would prevent the Bed Bug from returning to its harborage, and so it excretes the excess water, retaining only the nutrients and solids. This excreta causes black sticky marks to be left on surfaces near the resting sites.
Adult Bed Bugs usually have a lifespan of about nine months, but have been known to survive much longer during adverse conditions (they may enter a form of inactivity or hibernation if the temperature drops below 13 degrees Celsius for extended periods). Additionally, Bed Bug colonies have been shown to survive for very long periods without feeding, over a year in some cases. This is believed to be linked to certain altruistic feeding behaviors, and possibly an evolutionary development for exoparasites of migratory hosts such as birds.
The damage caused to the host by feeding is negligible, and the quantity of blood lost to feeding is not normally significant to well fed adults from developed countries (although this may not be the case for under-nourished hosts or young children).
(Video Credits: David Cain, Bed-Bugs.co.uk)
Bed Bugs are insects in the order Hemiptera (referred to as true bugs by scientists). All the members of this order have beak like piercing mouthparts which are used to suck a liquid diet. In most of the Hemiptera this is obtained from plants (they suck the plant sap), but in the parasitic bugs it is obtained from warm blooded animals (the blood of mammals and birds).
The saliva contains a number of important ingredients. They include an anticoagulant to ease feeding and ensure the hosts blood does not clot and block the mouthparts, an anesthetic to reduce the chances of a potentially fatal retaliation from the host, and enzymes to start the digestive process. This is significant, as these materials are all detected as foreign proteins by the host, and it is the hosts own immune reaction to these invading materials that causes the development of the itches and lumps associated with insect bites.
Bed Bugs, in common with many Hemiptera, possess a venomous bite that is quite distinct from their feeding bite. Bed Bugs are not normally aggressive and will not bite venomously unless seriously disturbed, but they have been known to do so when irritated by treatment with control chemicals. While rarely significant, the Bed Bugs venomous bite is described as very painful, and usually results in considerable swelling.
The common Bed Bug is not the only parasitic true bug that may be encountered. There are a few other relatives of the Bed Bug that have been described commonly biting man, and several others that do not feed on man but are found occasionally in human dwellings and may be confused with Bed Bugs.
Cimex hemipterus is very similar to the Bed Bug. C. hemipterus is confined to tropical regions (including Florida), but otherwise retains as much pest potential.
Cimex pilosellus and Cimex pipistrella are primarily parasites of bats. These species are sometimes found in structures where the host has taken residence (usually the roof space or a structural void), and may even be found entering the human areas of the structure if the host has vacated their roost. These species will not normally bite people, and the site of infestation is often a strong clue to the species.
Continue reading here: Biology & Life Cycle of a Bed Bug- BB ALERT
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Bed bugs life cycle
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