How can a tube as flimsy as a mosquito’s proboscis be stiff enough to act as a hollow boring tool? What is it made of and what is the typical wall thickness of this amazing auger? Also, what is the minimum capillary diameter through which blood could be sucked?
• There is a common misapprehension that a mosquito’s proboscis is used to pierce skin. The proboscis is no more than a glorified straw, used in males and females to feed on nectar and other plant juices.
A female mosquito needs blood nutrients before she can produce eggs, so her proboscis hides a variety of surgical tools. She will sniff out her target, preferably a sweaty, pregnant woman with blood group O and the genetic propensity to produce chemicals that mosquitoes find particularly attractive.
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When a female lands on you, she will find a suitable site with the tip of her proboscis, pressing it hard against your skin before deploying her weaponry through the tip. Two pointed mandibles and two bladed maxillae do the piercing and cutting. One tube – the hypopharynx – introduces anticoagulant saliva, along with any pathogens, and a second tube – the labrum – sucks up the blood.
Human monocytes, the largest type of white blood cell, can have a diameter of up to 20 micrometres, so I guess any mosquito with a narrower labrum would be less likely to pass on its genes.
David Muir, Edinburgh, Scotland
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