squitoes were buzzing around Earth long before humans arrived, but with billions of us across the globe, these insects have a buffet like never before. There’s now renewed concern over mosquito bites as the Zika virus persists, and the Rio Olympics are just months away. NRP station KQED and PBS have a new edition of Deep Look on YouTube that zooms in on the mosquito bites everyone is so concerned about, revealing the multifaceted blood-guzzling toolkit mosquitoes use to inadvertently spread disease.
The mosquito’s proboscis looks like a single needle-like appendage, but as the video below illustrates, it’s so much more than that. First, there’s a protective sheath that retracts when it’s time to suck some blood. That reveals six individual needles, each of which have a role to play.
The outer pair of needles are where the whole process of stealing your blood starts. These needles have tiny teeth like a saw blade. Female mosquitoes use these to saw through your skin and into the tissue where blood vessels can be found. The next needles in from those are used to hold the tissue apart so it can search for a blood vessel. That’s actually the job of one of the remaining two remaining needles. Receptors pick up chemical signals released by blood vessels to guide the tip in. Then, it’s time to vacuum up all the blood the mosquito can carry.
This is all annoying, but it’s the final needle of the six that really causes trouble for humans. It is this needle that injects a mixture of mosquito saliva and anticoagulants that keeps the blood flowing and numbs the site of injection. This is also what causes the itchy welts after the mosquito has flown off. The saliva is where nasty critters like Malaria parasites and Zika viruses can hide. The mosquito doesn’t have any reason to infect us, these organisms are just along for the ride.
It’s a marvel of evolution. Also, slightly terrifying.