Bed Bug Biology

Close-Up of a Bed Bug on Human Skin

Bed bugs (or "bedbugs" -- either form is correct) are small, reddish-colored, flattened, parasitic insects in the family Cimicidae, all of whom feed on the blood of their preferred hosts. In the case of the bed bug (Cimex lectularius), that preferred host happens to be human beings. Bed bugs feed exclusively on human blood, usually while the people they've adopted as hosts are sleeping.

Bed bugs are, of course, nocturnal, and their small size enables them to hide almost anywhere. They're commonly found in mattresses, box springs, all sorts of furnishing, structural cracks and crevices, the spines of hardcover books, hollow curtain rods, wall and ceiling voids, electrical fixtures and conduit... you name it.

Their small size and secretive, nocturnal habits make it entirely possible for a room to be infested for months without the occupants knowing it. Very often, the first sign of a bed bug problem is not the bed bugs themselves, but the blood stains on the bedding or the bite marks where the bed bugs were feeding. As their populations increase, bed bugs often travel through structural voids to other parts of a home.

In severe bed bug infestations, there may also be a putrid smell.

Bed Bug Life Cycle and Development

Bed Bug Life Cycle Chart

Bed bugs begin their existence as eggs, which female bed bugs lay in areas near where people sleep. Adult female bed bugs can lay as many as five eggs a day, and as many as 500 eggs during her lifetime, under ideal conditions. the eggs are glued to surfaces near where people sleep (such as on the mattress, box spring, or bed frame), and the eggs hatch seven to ten days later.

The newly hatched bed bugs are called "nymphs," and they are on their own from the day they hatch. Momma did her part by depositing the eggs near a place where humans sleep, and she provides no further care to the young bed bugs. From the day they hatch, all bed bugs (including both males and females) are exclusive blood feeders.

Bed bugs undergo incomplete metamorphosis, which means there are only three life stages: egg, nymph, and adult. The nymphal stage, however, is divided into five instar phases, during each of which the nymph must consume at least one blood meal before molting to the next phase (or ultimately, to the adult stage). It usually takes about two months for a bed bug to develop from egg to adult, but this can vary widely depending on temperature and food availability.

Bed bugs don't need to feed every day. If food is scarce, adult bed bugs can live for several months -- and possibly as long as a year -- without feeding. Even when human blood is readily available, individual bed bugs may go several days to a week between blood meals, spending the time in between mainly idle and in hiding.

Reasons For the Resurgence of Bed Bugs

For many years, bed bugs were rarely encountered in the United States and most other modern, industrialized nations, leading many people to wonder why have they suddenly become such a major public health pest. Entomologists believe that there are several reasons for the recent explosion of bed bugs in the the United States.

The first reason has to do with travel. More people than ever are traveling internationally as tourists, which means that there are more opportunities than ever for bed bugs to hitchhike in people's luggage and on their persons from bed bug-endemic areas.

Immigrants Being De-Loused, Early 20th Century

The second reason has to do with widespread concerns about louse-borne typhus that resulted in extensive "de-lousing" efforts during the early 20th Century. De-lousing of people and steam-cleaning of clothing and belongings were commonly performed on new immigrants, prisoners, armed forces recruits, and sometimes even schoolchildren. In addition, entire apartment buildings, shelters, and even hospitals (along with the people in them) were commonly treated for body lice if even one case was uncovered.

Although these efforts targeted body lice, not bed bugs, the insecticides used (such as DDT) were also effective against bed bugs, resulting in incidental control of bed bug populations.

The third reason reflects differences in the way we do pest control nowadays. Once upon a time, exterminators routinely sprayed homes and other buildings with powerful, broad-spectrum insecticides to control common household pests like ants and cockroaches, often followed by applying a "fog" intended to get into the cracks and crevices. Although bed bugs were not the target pest, the treatments killed them, nonetheless.

Nowadays, pest control treatments are more specific to the target pests, and are less effective (or not effective at all) against other insects. In addition, many insect pests like ants and cockroaches are commonly treated with baits, which are useless against bed bugs because they are blood feeders.

Finally, when people put off obtaining effective, professional bed bug control, they allow bed bug populations to grow and spread to adjacent rooms or apartments. Whether because of concerns about insecticides or to try to save money, many people waste time trying do-it-yourself bed bug control, which is almost never effective, rather than hiring professionals from the start. This allows small bed bug problems to grow into huge bed bug problems.

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