Why don’t bedbugs and fleas bite? - briefly
Bedbugs and fleas are hematophagous ectoparasites that actively pierce skin to obtain blood meals. Their specialized mouthparts enable efficient feeding, so they do, in fact, bite their hosts.
Why don’t bedbugs and fleas bite? - in detail
Bed bugs (Cimex lectularius) and fleas (Siphonaptera) are obligate hematophages; they feed on the blood of vertebrate hosts to obtain proteins and lipids essential for development and reproduction. Their mouthparts are highly specialized. Bed bugs possess a slender, needle‑like proboscis that pierces the epidermis, injects anticoagulant saliva, and draws blood. Fleas have a stylet bundle capable of cutting through the skin and a pump mechanism that creates negative pressure to ingest plasma.
Both insects demonstrate selective feeding behavior. Several physiological and environmental factors suppress biting activity:
- Host availability – Absence of a suitable warm‑blooded host reduces the stimulus for probing. In laboratory cultures without hosts, individuals may survive for weeks without feeding.
- Temperature – Optimal feeding occurs at 30‑35 °C. Ambient temperatures below 20 °C slow metabolism, delaying or halting blood‑seeking behavior.
- Humidity – Relative humidity under 50 % increases desiccation risk, prompting insects to conserve water rather than expose themselves while feeding.
- Reproductive state – After a recent meal, females enter a gonotrophic cycle lasting several days; during this period they are less motivated to bite.
- Chemical cues – Carbon dioxide, lactic acid, and body heat serve as attractants. Low emissions from a host diminish the likelihood of a bite.
When these conditions are unfavorable, the insects may remain in a quiescent state, seeking shelter in crevices or burrows until stimuli improve. Their survival strategies include prolonged fasting, reduced metabolic rate, and the ability to tolerate dehydration for extended periods.
In contrast, when a host presents the appropriate thermal, olfactory, and moisture cues, both species actively locate feeding sites, inject saliva containing anesthetic and anticoagulant compounds, and ingest blood. The bite itself is a brief mechanical event, typically lasting less than a second, followed by a prolonged period of digestion that can extend several days. This precise coordination of sensory detection, physiological readiness, and specialized morphology explains why biting occurs only under specific conditions and may appear absent when those conditions are not met.