The most common type of bed bug, and species known to prefer human blood, is the Cimex lectularius. Other species exist, but this one has adapted to human environments; their preferred habitats including heated homes or properties where they can infest beds and sofas.
The species is most active at night, often hiding during the day, although it is not uncommon to find active bed bugs in the day time. For this reason they are not exclusively classed as nocturnal.
Bed bugs are found across the globe, their existence having increased since the mid-1990s. This is mostly blamed on the increase in cheap air fares, allowing for more international travel, as well as the bed bug’s growing natural resistance to pest control chemicals.