Passage Four
No matter who you are or where you come from, one thing is certain：you are acquainted with the mosquito(蚊子)--although you probably wish you weren’t. Mosquitoes are everywhere. They can be found all over the world, and they come in more than 2,500 species. Somewhere, at some time, you have surely met at least one.
No one loves the mosquito. But unfortunately the mosquito may decide that she loves you. Yes, She. Only the female mosquito bites. It’s not because she’s unfriendly: she needs blood to reproduce. Female mosquito is quite selective, and she chooses her victims carefully. First, she uses sensors to find her victim. With these sensors, she tests your body moisture, body warmth, and chemical substances in your sweat. If she likes what she finds, she bites. But if you don’t appeal to her, she’ll reject you for someone more appetizing. The next time a mosquito bites you, just remember that you were chosen. You’re special.
If the mosquito likes you, she settles onto your flesh very gently, and she breaks your skin with her proboscis tip. It’s a kind of mouth and it sticks out just below the mosquito’s eyes. She stabs the proboscis tip into your skin at once, and if she hits a blood vessel, she’ll get a full dinner in about a minute. After that, the mosquito is tired. Heavy with your blood, she picks a spot---on a leave or a stone---to lay her eggs. Just one drop of blood will produce hundreds of eggs.

According to the last paragraph, the function of proboscis tip is to _______.