Expert Facts on Bed Bugs Provided by Pest Detective

Introduction

These blood-feeding bugs of the Family Cimicidae (the “Bed Bugs”) probably evolved as cave-dwelling ectoparasites of mammals (mainly bats) and birds. When our ancestors moved into those same caves, one group of the bugs apparently switched hosts and developed a “preference” for human blood. One species, the common Bed Bug (Cimex lectularius L.), became the most directly associated with humans. As our civilizations developed, these bugs moved with us into tents, and then houses; and they have remained a pest throughout recorded history. Since the wide-spread use of synthetic insecticides like DDT began, soon after World War II, bed bugs had become very rare pests. Although they have been sporadically noted worldwide, they seemed to have nearly disappeared in developed countries. Many current Pest Management Professionals (PMPs) in Canada and the U.S. with as long as 10 years on the job may have never actually seen an active bed bug infestation. However, in the past five years, bed bugs have been making a progressively more rapid come-back. Several regional technical experts have been reporting them more and more often in homes, hotels, hostels and long-term care facilities in the past two years.

Description

Bed bugs are small, about 3/16 inch (4-5 mm.) long, broadly oval, flat, brown to reddish-brown insects. They are true bugs (Order: Hemiptera), with a 3-segmented beak, 4-segmented antennae and vestigial wings. They have very thin, vertically-flattened bodies covered with short, golden-coloured hairs. Males have somewhat pointed abdomen tips; females and older nymphs have broadly rounded abdomen tips. When fully engorged, a bed bug’s body looks like a dark oblong balloon. Characters contained in pictorial keys in several common Pest Management references, such as Mallis’ Handbook and the NPMA Field Guide, and a 10X hand lens, can help PMPs accurately identify (ID) these pests to species. Rapid, correct ID, in turn, is essential to effectively controlling them.

Biology

Bed bugs feed only on blood, usually from mammals or birds. Mating is by “traumatic insemination,” a strange behaviour in which a male pierces a female’s abdomen and injects sperm into a layer of fatty material in her body cavity. Their life cycle, under good conditions, (75-80% RH; 83-90oF), takes four to five weeks (egg-to-egg). They attach their small (about 1 mm long) pearly-whitish eggs to surfaces, usually in crevices (harborages) where the bugs hide in loose groups or clusters. They have five nymphal instars, needing at least one blood meal for each instar to develop to the next instar. A female may lay 200-500 eggs in her lifetime. These bugs will often produce a series of bites in “rows,” or fairly straight lines, usually along an edge beside an item of clothing or a bed sheet which was lying against their human host’s skin at the time the bugs fed. Bed bugs give off a distinctive, “musty, sweetish” odour, which may be obvious to many humans’ sense of smell, where a number of bugs have congregated in a shared harborage. Fewer than 50 adult bugs (based on actual collected specimens), along with their offspring, present for no more than a few weeks, have been observed to produce such a detectable odour. They routinely deposit partially digested remnants of prior blood meals in their hiding places, as a “rusty” or tarry residue.

Habits

Bed bugs are nocturnal, hiding in cracks, crevices, mattress tufts, seams, or in hollow furniture legs. It may take three to ten minutes for one bug to feed until full. Bugs will sometimes (less than 25% of the time) “excrete” remains of their last partially digested blood meal while feeding the next time. This is the cause of the typical “rusty” spots seen on bed clothing in many infested homes. They will feed repeatedly, but MUST have at least one blood meal in each instar to develop to the next instar. Despite the myth that bed bugs become inactive (go into “hibernation”) at temperatures below 61°F (= 16°C), a colony started from specimens wild-caught in New Jersey in 1973 has remained very active, feeding aggressively, at temperatures as low as 45°F (7.2°C ). Similar low-temperature bed bug activity was observed by Wigglesworth (1984). These bugs will readily travel 10-15 ft., and have been observed to travel more than 100 ft., from their established harborage (and back) to feed on a host. Although they seem to “prefer” humans, bed bugs very readily feed on birds, rodents or other mammals.

Medical Importance

True bed bugs have been found naturally infected by more than 20 human pathogens, but have never been proven to biologically transmit even one human pathogen. Although their bite is often nearly undetectable, their saliva contains several proteins which can cause a progressive sensitivity to repeated bites (typically five stages of: no reaction, delayed reaction, delayed and immediate reactions, immediate reaction only, and finally no reaction; depending on the combined biting intensity and frequency). Sometimes, humans who are frequently bitten by these bugs may develop a sensitivity ‘syndrome’ which can include nervousness, nearly constant agitation (“jumpiness”) and sleeplessness. In such cases, removing either the bed bugs (by physical or chemical elimination), or relocating the person, has usually caused the syndrome to disappear in less than a month. Several different species of Cimicidae may bite humans, including tropical bed bugs, poultry bugs and several species of bat bugs. Adults can live for several months (in some reports, for more than one year.) and nymphs for at least three months without feeding. There is often a serious social “stigma” to having an infestation of these bugs.

Some possible reasons for the observed resurgence of bed bugs as pests include:

• Greatly increased human mobility (frequent career changes, rapid long-distance travel, widely-dispersed families, etc.), along with much less attention to quarantine programs by most governments, has made it more possible (and probable) for these (and related) bugs to be spread quickly to every country, city, or home; and across all social and economic strata.
• Incorrect initial ID and (usually) grossly inadequate initial surveillance, before any treatment, may lead to killing only part (often only a small part) of the population which is actually present.
• Less use of any residual pesticides, especially non-repellent types, in areas bed bugs usually infest.
• There has been a significant recent switch to mainly using baits for controlling cockroaches and similar pests. Since these bugs only feed on blood, the baits usually do not even contact, and thus do not affect them.
• In the past several years, most PMPs have switched to using primarily pyrethroids for nearly all indoor residual pesticide treatments. Many of these pyrethroids are very repellent, and could often cause the bed bugs’ population(s) to “split up,” spread out, or at least move to one or more new locations.
• The public knows very little about bed bugs, their biology, or their control (or prevention). Unfortunately, many laymen, some doctors, and even a few PMPs may blame “bed bugs” for any ‘bite symptoms’ which they can’t explain, or for which they can’t seem to find any other definite cause.
• A natural population increase. All animals exhibit increases and decreases in populations over time.