Hidden within this mosquito’s straw-like proboscis is a tube with a very sharp tip designed for piercing skin.

House Fly. (Julia Wilkins / Wiki; CC**

The blood of a human volunteer can be seen filling the abdomen of this mosquito, Armigeres subalbatus, as she feeds. (James Gathany, CDC; PD)

Compound eyes of a fly.
(© Bryan Faust / iStock)

House Fly (Musca domestica). (Julia Wilkins / Wiki; CC BY-SA 3.0)

Mosquito larvae live in water (shown here: Culex sp. (James Gathany / CDC; CC BY 2.5)

House Fly (Musca domestica). (Tom Murray / BugGuide; CC BY-ND-NC 1.0)

Head of a long-legged fly (Family: Dolichopodinae). (Donald Jusa / Flickr; CC BY 2.0)

Pretty Picture-winged Flies are fruit flies. Shown here: Chetostoma curvinerve. (gailhampshire / Flickr; CC BY 2.0)