Anyone who has tried to thread an i.v. or insert a Vacutainer needle into a small vein will appreciate the skill demonstrated by a mosquito as its mouthparts probe under the skin searching for the vasculature.
From afar, a mosquito’s snout might look like a single tube, but it’s actually a complicated set of tools, encased in a sheath called the labium. You can’t see the labrum at all in the videos; it buckles when the insect bites, allowing the six mouthparts within to slide into the mouse’s skin.Further details at the incomparable Not Exactly Rocket Science blog at National Geographic.
Four of these—a pair of mandibles and a pair of maxillae—are thin filaments that help to pierce the skin. You can see them flaring out to the side in the video. The maxillae end in toothed blades, which grip flesh as they plunge into the host. The mosquito can then push against these to drive the other mouthparts deeper.
The large central needle in the video is actually two parallel tubes—the hypopharynx, which sends saliva down, and the labrum, which pumps blood back up.