COMMENTS:

Are some of the worst pest species known for humans and livestock not all species bite humans
Transmit diseases such as filarial nematode infections, various viruses and avian protozoan parasites
Uniquely shaped with a swollen abdomen with a caudal sucker that allows for attachment to substrate
Labrum is modified into a fan-like structure with brush of hair which is used for filter feeding
Most species are filter feeders as larvae so they are more or less restricted to lotic habitats from small springs to large rivers Live attached to substrate of some sort species feed on diatoms and green algae and detritus
Some species are predators and their mouthparts are modified for grabbing prey (http://www.biology.eku.edu/SCHUSTER/bio%20806/diptera.htm)