Bed bugs are small, parasitic insects belonging to the family Cimicidae. They are flat, oval, and reddish-brown, feeding exclusively on blood throughout all stages of development. While many people assume there is only one type, the term applies to several distinct species within the genus Cimex that can infest human dwellings. This diversity means that identification and successful removal often depend on knowing exactly which variety has taken up residence.
The Common and Tropical Bed Bugs
The majority of human infestations worldwide are caused by two species: the Common Bed Bug (Cimex lectularius) and the Tropical Bed Bug (Cimex hemipterus). Historically, the Common Bed Bug dominated temperate regions, while the Tropical Bed Bug was confined to warmer, humid climates like Africa, Asia, and South America. Both species are highly specialized to feed on human blood.
The widespread use of insecticides after World War II temporarily suppressed both species. A significant global resurgence began in the 1990s due to increased international travel and insecticide resistance. This resurgence has blurred their traditional geographic boundaries. The Tropical Bed Bug is now expanding its range, appearing in regions like the Middle East, Europe, and the southern United States.
Related Species That Infest Homes
Beyond the two main human pests, several other species in the Cimex genus can occasionally bite humans. These varieties are primarily associated with non-human hosts but are often mistaken for the common bed bug when they venture into living spaces. They become opportunistic feeders when their preferred hosts, such as bats or birds, abandon their nests within a structure.
Bat Bugs, including Cimex adjunctus, normally feed on bats roosting in attics or wall voids. If the bat colony leaves, these bugs lose their food source and may migrate into the home seeking a blood meal from humans. Bird or Poultry Bugs, such as Cimex columbarius, parasitize birds nesting on a building. When the birds migrate, these bugs may enter human rooms and bite people.
Identifying Characteristics and Global Range
Distinguishing between these species is challenging because they are similar in size, color, and behavior. Subtle morphological differences exist, particularly on the thorax. The most reliable way to differentiate the Common Bed Bug from the Tropical Bed Bug is by examining the shape of the pronotum, the plate-like segment behind the head.
The Common Bed Bug’s pronotum is deeply excavated or notched, giving it a more flared appearance. In contrast, the Tropical Bed Bug’s pronotum is shorter and less deeply notched. This difference is quantifiable, as the width-to-length ratio of the pronotum is significantly higher in the common species.
Identifying a Bat Bug from a Common Bed Bug is even more difficult, often requiring microscopic examination. Bat Bugs like Cimex adjunctus are distinguished by having longer fringe hairs on their body, especially those located on the sides of the pronotum. These hairs are generally equal to or longer than the width of the bug’s eye, a feature that is shorter on the Common Bed Bug.
The location of the infestation offers a practical, non-microscopic clue to the species involved. If the bugs are found concentrated around the bed, mattress seams, or near-bed furniture, it strongly suggests the Common or Tropical species. Finding bugs primarily near the ceiling, windows, or in rooms adjacent to an attic or chimney, however, indicates a Bat Bug or Bird Bug infestation. This is because the latter species remain close to their primary hosts’ nesting sites.