Ed Yong at Not Exactly Rocket Science covers some awesome microscopic footage of a mosquito biting a mouse, revealing how the mosquito's proboscis carefully probes tissue until it hits a capillary.
This footage was captured by Valerie Choumet and colleagues from the Pasteur Institute in Paris, who watched through a microscope as malarial mosquitoes bit a flap of skin on an anaesthetised mouse. The resulting videos provide an unprecedented look at exactly what happens when a mosquito bites a host and drinks its blood.
Ed wryly notes:
When a mosquito finds a host, these mouthparts probe around for a blood vessel. They often take several attempts, and a couple of minutes, to find one. And unexpectedly, around half of the ones that Choumet tested failed to do so. While they could all bite, it seemed that many suck at sucking.
Unfortunately (for bite victims), mosquitoes infected with Plasmodium will spend more time probing for blood vessels "which presumably increases the odds that the parasites will enter a new host.". The underlying reason for this change in behaviour is yet to be confirmed but Ed suggests that the parasite may be modifying the mosquito's nervous system or its gene activity of its mouth parts.