Source: The Verge, Jun 2016
The thin tube the insect injects into the skin, what’s called the proboscis, is actually comprised of six different needles that all work in tandem to extract blood from the body.
The first two needles act a bit like teeth, the video shows. The have tiny ridges at the end that help the mosquito puncture through the skin.
A second pair of needles act like clamps during the blood draw, holding the skin’s tissues apart to allow the last set of needles to do their work. Among these is a needle that acts like a homing beacon; it finds our blood vessels by detecting the chemicals they give off, and then slurps up the tasty blood inside.
The last needle is the real jerk: it injects chemicals into our vessels to stimulate blood flow. But it’s also what makes those itchy bumps appear after the mosquito gets its fill and leaves. All of these needles are then shielded by a flexible sheath called the labium.