Siphonaptera - (fleas)
This is a small order of wingless insects with around 3000 species. The adults are laterally compressed and move by jumping. They are blood-sucking ectoparasites of warm-blooded animals which can transmit diseases like the plague. The larvae are worm-like and feed on the feces of the adult fleas as well as other organic matter.
For details see the respective page in Wikipedia.
The following families are currently included under Siphonaptera: