Kissing bugs, scientifically known as triatomine insects, are blood-feeding pests found predominantly in the Americas. Many species can transmit the parasite Trypanosoma cruzi, which causes Chagas disease. These nocturnal insects must locate a host to survive. Understanding the specific cues that draw them toward human dwellings is the first step in managing their presence, including their biological need for a blood meal, safe daytime shelter, and artificial light sources.
Biological Cues: Heat, Carbon Dioxide, and Host Odors
Kissing bugs detect the signs of a sleeping mammal using sensory tools to find a host for a blood meal. The most significant cue is the carbon dioxide ($\text{CO}_2$) exhaled during breathing, which indicates the presence of a vertebrate host. Studies show that some nymphs orient toward airstreams containing $\text{CO}_2$ levels of 1,600 to 3,200 parts per million (ppm), significantly above ambient air concentrations.
As the bug gets closer, it uses thermal signatures to pinpoint the source of heat. Kissing bugs are attracted to warm temperatures, a reliable signal of an endothermic host like a human or a pet. This warmth is important for initiating the final biting and feeding sequence.
Host odors also play a role, often working synergistically with $\text{CO}_2$ to increase attraction. Specific compounds released from skin and breath, such as ammonia, L-(+)-lactic acid, and hexanoic acid, are important short-range attractants. The combination of these odors and $\text{CO}_2$ lowers the threshold at which the insects respond to the gas alone, making the host’s scent profile highly effective.
Structural Harboring Sites Near Human Dwellings
Kissing bugs require dark, secure locations to spend the daylight hours and complete their life cycle. They generally live in close proximity to a blood host, making domestic structures highly attractive as harborages. In natural settings, they hide in the nests and burrows of wild animals like woodrats, opossums, and raccoons.
Near a home, they seek protective environments that provide crevices and clutter. Common outdoor harborages include piles of wood, brush, or rock, beneath porches, or between rocky structures. These sites offer shelter from predators and the elements, and often contain nests of small mammals that serve as a persistent blood source.
Poorly sealed homes offer direct entry points and indoor harborage that mimics their natural habitat. Cracks in foundations, gaps in walls, and openings around windows and doors allow access to crawl spaces and attics. Once inside, they hide in dark places, such as behind pictures, near mattresses, in beds, or close to pet resting areas. The presence of wingless nymphs inside is a strong indication that a breeding population has established a nearby harborage.
Influence of Outdoor Lighting
While heat and $\text{CO}_2$ are primary mechanisms for host-seeking, adult kissing bugs are also drawn to artificial light at night, which can inadvertently lead them to a home. This attraction is a form of positive phototaxis, or movement toward light. Since they are nocturnal and can fly, adults may take flight in search of new hosts and be drawn by bright exterior lights.
Specific wavelengths of light are more attractive to kissing bugs than others. Research on Triatoma rubida showed adults were most attracted to light with a wavelength of 470 nanometers, which falls in the blue spectrum. Lights that emit in the blue or ultraviolet range are generally more attractive to night-flying insects than those with longer wavelengths, such as yellow or amber. When lights are located near entryways, the attracted insects can easily enter the home through open doors, windows, or small gaps.
Mitigation Based on Attractants
Managing kissing bug attraction involves an Integrated Pest Management (IPM) approach that counters the cues and harborages that draw them in. To reduce biological attractants, deny them access to the home environment where humans and pets sleep. This is achieved by sealing all potential entry points into the structure, including gaps around doors, windows, and utility conduits.
Addressing structural attractants involves removing protective daytime harborages near the house. Woodpiles, rock piles, and debris should be moved away from the foundation and stored off the ground. Since many species are associated with wild animal nests, eliminating nesting materials and burrows of rodents, opossums, or raccoons near the home perimeter is beneficial.
To reduce light attraction, modify or eliminate exterior lighting after dark. Replacing bright white or mercury vapor lights with yellow, amber, or low-UV light-emitting diode (LED) bulbs can decrease the number of insects attracted. Drawing curtains or blinds at night and moving interior lights away from windows and doors reduces visible light cues that might pull them toward the house. Keeping pets indoors at night, particularly in well-sealed areas, reduces host availability and prevents the bugs from being carried inside.