Overview
Fleas (order Aphaniptera) are small, wingless, jumping, blood-sucking insects that parasitise mammals and birds. Medically they matter as the vectors of plague and murine typhus; this note also covers the other human ectoparasites, lice and bedbugs.
Characteristics of the order Aphaniptera
Fleas are 1.5–4 mm long, wingless, dark brown insects whose body is flattened from side to side (laterally compressed), so that they slip easily between hairs and feathers. Backward-pointing bristles and, in many species, combs (ctenidia) hold them in the fur. The mouthparts are piercing-sucking, and the long hind legs make them powerful jumpers.
Development is by complete metamorphosis: egg, larva, pupa and adult. The worm-like larvae live free in nests and bedding and feed on organic debris and the faeces of adult fleas; the adult emerges from the pupa when it senses the vibration or warmth of a host. Only the adult feeds on blood, and it bites several times a day.
- Pulex irritans: the human flea.
- Xenopsylla cheopis: the oriental rat flea, the main plague vector.
- Ctenocephalides felis and C. canis: cat and dog fleas, which also bite humans and carry Dipylidium caninum.
- Tunga penetrans: the sand flea (chigoe), whose pregnant female burrows into the skin of the feet and causes tungiasis.