How do bedbugs locate a human? - briefly
Bedbugs detect humans by sensing carbon dioxide, body heat, and specific skin odor compounds. Specialized sensory organs called sensilla interpret these cues and guide the insects toward the host.
How do bedbugs locate a human? - in detail
Bedbugs rely on a combination of sensory cues to find a suitable host. Their detection system integrates thermal, carbon‑dioxide, olfactory, and vibrational signals.
The primary attractant is body heat. Specialized thermoreceptors on the antennae and legs sense temperature gradients as low as 0.1 °C. When a heat source exceeds ambient temperature by 2–3 °C, the insects orient toward it, moving up the gradient until they reach the skin surface.
Carbon‑dioxide released by respiration serves as a long‑range cue. Lab experiments show that concentrations of 400–500 ppm trigger increased activity, while levels above 1 % provoke rapid forward movement. Bedbugs possess CO₂‑sensitive sensilla on the maxillary palps that detect rising plume concentrations and guide the insect in the direction of the source.
Odorants emitted by human skin, sweat, and sebum provide short‑range confirmation. Volatile compounds such as lactic acid, ammonia, and fatty acids bind to olfactory receptors on the antennae. Electrophysiological studies demonstrate heightened neuronal firing when these chemicals are presented, prompting the bug to initiate probing behavior.
Mechanical vibrations generated by movement or breathing are sensed by mechanoreceptors on the tarsi. Vibration amplitudes as low as 0.01 mm trigger a startle response, causing the bug to pause and re‑assess the location of the host.
The sequence of host‑locating behavior typically follows these steps:
- Long‑range detection: CO₂ plume and heat gradient draw the insect from hiding places.
- Intermediate navigation: Temperature and odor gradients refine the path toward the body.
- Close‑range confirmation: Skin‑derived volatiles and subtle vibrations verify the target.
- Attachment: The bug probes the skin with its rostrum, initiates feeding, and returns to the shelter.
Each sensory modality operates concurrently, allowing rapid and accurate host identification even in low‑light conditions. The integration of these cues explains why bedbugs can locate humans efficiently despite their limited mobility.