There are two main species of bed bugs: Cimex lectularius (the common bed bug which occurs world-wide) and Cimex hemipterus (the tropical bed bug). In West Africa, Leptocimex bouetti attacks man. Bed bugs are insects (4-7 mm) with rudimentary, non-functional wings. This limits their capacity for dispersion. They are not vectors of pathogenic organisms, but are primarily a nuisance because of their behaviour. They suck blood for a short time during the night or at dawn. During the day the adult insects hide in all sorts of cracks and crevices. They can fast for a very long time (>1 year in the laboratory). When the environmental temperature drops below 15°C, they become inactive. Often dirty brown spots caused by their faeces are found on sheets, walls or floors. Females lay 6-10 eggs per week, usually in the place where they spend the day. Sometimes clusters of hundreds of 1 mm large whitish-yellow eggs can be seen on walls, under wallpaper, etc. Their further development is heavily influenced by temperature and moisture. At room temperature, eggs hatch after 15-22 days. After about 6 weeks, adult insects appear. Temperatures higher than 45°C maintained for 30' kill the insects. After a bite, a severe pruritic skin reaction can occur. Spraying insecticides helps control these animals.