I used to picture mosquitoes liked winged hypodermic needles, jabbing their rigid, needle-like mouthparts into flesh and slurping blood. But it turns out this view was wrong: Their snouts are surprisingly mobile and flexible, and can bend almost 90 degrees once inside the body to search for blood.
As you can see in the video below, which I stumbled across on Ed Yong's blog Not Exactly Rocket Science, the mouthparts contain multiple parts that diverge once entering flesh. "Four of these — a pair of mandibles and a pair of maxillae — are thin filaments that help to pierce the skin," Yong writes. And the main brown filament is made up of two parallel tubes: a hypopharynx, which emits saliva, and a labrum, which pumps blood back up.
The video was made with a microscope inserted into the skin of an anaesthetized mouse, which was then fed upon by malaria-infected mosquitoes, Yong writes. You can see the mosquito searching around before finally hiting a vein.