In parasitic bloodsucking forms the mandibles often have the shape of piercing stylets, and are enclosed in a tubular proboscis formed by the union of the upper lip (labrum) with the lower lip (hypostome or paragnatha).
- Head of Bloodsucking Vampire (Desmodus rufus).
The proboscis of tsetse-flies is without the paired piercing stilets (mandibles and maxillae) possessed by other bloodsucking Diptera, such as the female horse-flies and mosquitoes.
In many bloodsucking flies, for example, the galea is absent, while the lacinia becomes a strong knife-like piercer and the palp is well developed.
The recent discovery of a bloodsucking maggot, which is found in native huts throughout the greater part of tropical and subtropical Africa, and attacks the inmates when asleep, is of great interest.