How much time does a mosquito take to penetrate the human skin?

From being bitten thousands of times I would say less than a second.

@MrGV I think,It depends on the type ,size& strength of mosquitoes.

I guess 2–3 seconds. The first second you’ll only feel some itches,the next second will depend on what you’ve described above,and the type/thickness of your skin(more fat more time to penetrate).

Longer than you think

The female mosquito has a specialised apparatus to penetrate the skin of its victim. At the end of the slender proboscis, there are two pairs of cutting stylets that slide against one another to slice through the skin. Once through the skin, the mosquito’s proboscis begins probing for a tiny blood vessel. If it does not strike one on the first try, the mosquito will pull back slightly and try again at another angle through the same hole in the skin. Inside the proboscis are two hollow tubes, one that injects saliva into the microscopic wound and one that withdraws blood. The mosquito’s saliva includes a combination of antihemostatic and anti- inflammatory enzymes that disrupt the clotting process and inhibit the pain reaction (so that the victim is unaware of the bite!)

“to penetrate the human skin”, probably what @MrGV said.

To do what @SkulpTor said (the whole process, not just the penetration itself), probably what @Doctor_D said.

There are several different types of mosquitoes, so I also agree with @blinkErri that it may vary slightly (imperceptibly) from type to type.

Mosquitoes SUCK!