How do street fleas bite? - briefly
Street fleas attach to the host, pierce the epidermis with their serrated stylets, and draw blood while injecting saliva that contains anticoagulants. The saliva induces localized itching and inflammation.
How do street fleas bite? - in detail
Street fleas attach to a host by sensing heat, carbon‑dioxide, and movement. Once on the skin, the flea uses its specialized mouthparts—composed of a hardened, serrated stylet and a flexible, needle‑like labrum—to pierce the epidermis. The stylet cuts through the outer layer, while the labrum creates a narrow channel that reaches the superficial capillaries.
During penetration, the flea injects saliva containing anticoagulants, enzymes, and anesthetic compounds. Anticoagulants prevent clot formation, allowing continuous blood flow; enzymes break down tissue proteins, and anesthetic agents reduce the host’s immediate sensation of the bite. Blood is then drawn up through the proboscis by a combination of muscular contractions and capillary action.
The feeding cycle proceeds as follows:
- Detection: Heat and CO₂ gradients guide the flea to a suitable spot.
- Penetration: Stylet punctures skin; labrum forms a feeding canal.
- Saliva injection: Anticoagulant and anesthetic substances are released.
- Blood ingestion: Flea consumes blood for several minutes, often alternating between feeding and resting phases.
- Detachment: After engorgement, the flea releases its grip and seeks another site or host.
Host reactions stem from the injected saliva. Histamine release triggers localized swelling, redness, and itching. In some individuals, the immune response intensifies, producing larger wheals or secondary infection if the skin is scratched.
Fleas can bite repeatedly because each feeding episode does not exhaust their abdominal capacity; they can ingest multiple meals before needing to molt. Their ability to survive on limited blood supplies enables them to remain active in urban environments where host encounters are intermittent.