Why don't bedbugs drink all the blood? - briefly
Bedbugs ingest only a small portion of a host’s blood because their mouthparts can extract limited volumes before they become engorged, and taking more would hinder mobility and raise the chance of detection. Their feeding strategy balances nutrient acquisition with survival by restricting the amount taken in each bout.
Why don't bedbugs drink all the blood? - in detail
Bedbugs obtain nourishment by piercing the skin of a sleeping host and injecting saliva that contains anticoagulants. The insect’s mouthparts can ingest only a limited volume, typically 0.2–0.5 µL per feeding session. This capacity is constrained by the size of the abdominal cavity, which expands modestly to accommodate the blood meal before the cuticle becomes distended.
After a meal, digestion proceeds over several days. Enzymes break down hemoglobin, releasing nutrients that are stored as lipids and proteins. Metabolic demand does not require the entire blood supply; a single engorgement provides enough energy for multiple days of activity and for the production of eggs. Consequently, the insect does not need to empty the host’s circulatory system.
Partial feeding also reduces the risk of host detection. Continuous or excessive blood removal would cause noticeable swelling, irritation, or a drop in blood pressure, prompting the host to awaken and potentially eliminate the parasite. By limiting intake, the bug maintains a low profile and can return for subsequent meals.
Additional physiological factors limit consumption:
- Salivary anticoagulants: They prevent clotting only for a short period, after which blood coagulates and becomes inaccessible.
- Osmoregulation: Excess fluid would overload the excretory system; the bug excretes excess water as urine during the post‑feeding period.
- Reproductive cycle: Females require a blood meal to develop eggs, but the quantity needed is fixed; surplus blood offers no reproductive advantage.
In summary, the insect’s anatomical capacity, metabolic requirements, defensive strategies against host response, and physiological constraints collectively explain why it does not ingest the entire blood volume during a feeding event.