The bat bug (Cimex pilosellus or Cimex adjunctus) is an ectoparasite belonging to the Cimicidae family, making it a close relative of the common bed bug (Cimex lectularius). These insects are obligate blood feeders, meaning they must consume blood to survive. Although they prefer bats as their primary host, bat bugs opportunistically bite humans, often leading to confusion and misidentification. Clarifying the distinctions between these species is important, as successful removal requires different strategies.
Physical Characteristics
The adult bat bug is a small, wingless insect, typically measuring 4 to 5 millimeters in length, comparable to an apple seed. Its body is flat and broadly oval-shaped, allowing it to easily hide in tight cracks and crevices. Before feeding, the insect’s color is generally a light tan to reddish-brown hue.
Once a bat bug has consumed a blood meal, its abdomen swells noticeably, and its color darkens to a deep mahogany or reddish-purple. Bat bugs possess piercing-sucking mouthparts that form a beak-like structure used to penetrate the host’s skin. Their overall appearance is so similar to a bed bug that visual differentiation by an untrained eye is nearly impossible.
The Source: Bats and Roosts
Bat bugs are nidiculous parasites, meaning they inhabit the host’s nest or roosting area rather than living on the host continuously. Their preferred habitat is within structures where bats establish colonies, such as attics, chimneys, wall voids, and behind eaves. They remain near the roost, emerging only to feed on the bats when they are resting.
The primary reason bat bugs enter human living spaces is the absence or removal of their bat hosts. If a bat colony dies off, migrates, or is excluded from the structure, the bugs lose their food source. Starving bat bugs then migrate down from the attic or wall voids into lower floors in search of a new warm-blooded host. They can survive for extended periods without a blood meal, allowing them time to traverse a building.
Distinguishing Bat Bugs from Bed Bugs
While bat bugs and bed bugs appear nearly identical to the naked eye, a distinct morphological difference requires magnification for confirmation. The most reliable way to differentiate the two species is by examining the length of the fringe hairs, or setae, located on the insect’s thorax (the pronotum).
In the bat bug, these hairs are noticeably longer, measuring at least the same length as the width of the insect’s eye. Conversely, the common bed bug has much shorter, sparser hairs on its thorax, which are significantly shorter than the width of its eye. This subtle difference is the feature professional entomologists use to definitively identify the species. Correct identification is important because misdiagnosing the infestation will lead to failed treatment, as the primary source will remain unaddressed.
Necessary Steps for Removal
Effective removal of a bat bug infestation is sequential, beginning with the elimination of the source. The initial step is the exclusion and removal of the bat colony from the structure. This process involves identifying all entry points the bats use and sealing them, often using one-way exclusion devices that allow bats to leave but not re-enter.
Pesticide treatment should only be initiated after the bats have been successfully removed, as the sudden absence of the host forces the bugs out of their hidden harborage areas. A professional pest control operator must then apply targeted residual insecticides and insecticidal dusts. These applications focus on the areas of original bat activity, such as attics, wall voids, and the pathways the bugs used to descend into the home. Treating only the living areas without addressing the roost will result in the continual emergence of new bugs.