Background Biology and bionomics

Public Health Significance of Urban Pests Bedbugs 133 132 to five weeks under good conditions – that is, 75–80 relative humidity and 28–32°C. They can survive and remain active at temperatures as low as 7°C, if they are held at an intermediate temperature for a few hours, but the temperature point of thermal death for them is 45°C Wigglesworth, 1984. T hey have five nymphal developmental stages instars, each needing at least one blood-meal to develop to the next instar. Bedbugs are nocturnal, but they will feed in full daylight when hungry. Females attach their small whitish eggs about 1 mm long to substrate surfaces, often in the crevices where they may hide in loose groups or clusters. Each female may lay 200–500 eggs in her lifetime, which may be 2 years or longer. Like fleas, these bugs often produce a series of bites in so-called rows or in fairly straight lines, usually along the edge beside an item of clothing or a bed sheet that was lying against their human host’s skin at the time the bugs fed Usinger, 1966; Krinsky, 2002.

4.1.3. Distribution in Europe and N orth America

The common bedbug can be found in all the temperate areas of the world – almost any- where people have established dwellings and cities. They thrive in conditions of tempe- rature and humidity that are considered comfortable for most people, and those same people usually provide them with ample blood-meals and plenty of choice harbourage nearby. The tropical bedbug, C. hemipterus, is distributed broadly throughout tropical and subtropical regions around the world, both north and south of the equator, but it requires a higher average temperature than does the common bedbug for its normal development and biological functions. It is seldom found in established infestations in continental Europe and is rarely found north of Mexico and Puerto Rico in the western hemisphere; however, occasional limited populations have been found in Florida. Several species of bat bugs Cimex spp. and swallow bugs Oeciacus spp. that may bite people are well established in most temperate areas of both Europe and North America Usinger, 1966.

4.1. Overview of the biology, bionomics and distribution of bedbugs

4.1.1. Background

The common bedbug Cimex lectularius, two tropical bedbugs Cimex hemipterus and Cimex rotundatus and a few closely related species of blood-feeding true bugs Hemiptera: Cimicidae have been persistent pests to people throughout recorded history. They may have evolved as cave-dwelling ectoparasites of mammals especially bats. As people moved from caves into tents, and then into houses, these bugs, especially the common bedbug, were probably brought along, too. With the widespread use of synthetic insec- ticides soon after the Second World War, bedbugs became very rare pests in many indus- trialized countries. By 1997, this species was so scarce in Canada, much of Europe and the United States that it was hard to find fresh specimens to use in teaching entomology clas- ses Snetsinger, 1997. Similar trends had been reported earlier for the United Kingdom, with a relatively constant or slightly declining level of public requests for control from 1967 to 1972 Cornwell, 1974. Many current PMPs with 10 years of experience may never have even seen an active bedbug infestation. During the past eight years, a definite resur- gence of common bedbugs has been reported in parts of Africa, Australia, Canada, some European countries and the United States. Sites infested by them have included homes, hotels, hostels and long-term care facilities Cooper Harlan, 2004; Doggett, Geary Russell, 2004; Hwang et al., 2005; Johnson, 2005. The authors have also observed bed- bug infestations in university dormitory housing.

4.1.2. Biology and bionomics

Adults of the common bedbug are about 6–7 mm long, broadly oval, flat, brown to reddish-brown true bugs, with a three- segmented beak, four-segmented anten- nae, and vestigial wings Fig. 4.1. They are flattened dorsoventrally and covered with short, golden hairs. T he bedbug gives off a distinctive, musty, sweetish odour, consisting mainly of various alde- hydes such as trans-hex-2-enal, trans-oct- 2-enal, which are produced by the defen- sive gland system located ventrally on the metathorax Weatherston Percy, 1978. They usually deposit undigested parts of earlier blood-meals in their hiding places, as a seemingly tar-like or rusty residue. Their abdomen tips are usually pointed in males and are more rounded in females Fig. 4.2 and Fig. 4.3. Bedbugs feed only on blood, usually of mammals or birds, and mate by so-called traumatic insemination Usinger, 1966; Stutt Siva-Jothy, 2001. Their life-cycle, from egg to egg, may take four Fig. 4.1. Shape and characteristics of the bedbug Source: Photo by H. Harlan. Fig. 4.2. Male bedbug abdomen, showing pointed characteristics of reproductive parts Source: Photo by H. Harlan. Fig. 4.3. Female bedbug, showing characteristic roun- ded abdomen Source: Photo by H. Harlan. Public Health Significance of Urban Pests 135 Gbakima and colleagues 2002 reported a very high prevalence of both common and tro- pical bedbugs up to 98 of rooms infested in camps for internally displaced persons in Freetown, Sierra Leone. In Australia, a government public health agency reported a 400 increase in bedbug complaints submitted during 2001–2004, compared with 1997–2000. They also reported increased interceptions of bedbugs mainly in luggage by national quarantine inspectors from 1986 to 2003, with 74 of those occurring from 1999 to 2003 Doggett, Geary Russell, 2004.

4.2.4. Other species of Cimicidae that can affect people