To be able to pierce our skin and suck blood out of our blood vessels mosquitoes have developed quite complex mechanism. This again proves that mosquitoes are not that simple insects as we might think. All the biting organs are located in the head of mosquito. The blood sucking is done only by female mosquitoes, because blood contains proteins that female mosquitoes need for egg development and male mosquitoes do not bite us. Because of this, female mosquitoes need special mouth parts to be able to pierce skin and pump blood from blood vessels. Mosquitoes actually need sugar to take energy, so male and female mosquitoes drink fluids that contain sugar from flowers and other plants.
Mosquito mouth parts
The best visible organ of mosquito mouth parts is the proboscis, which consists from multiple other mouth parts that can only be seen with a microscope. Just by looking at the trunk of a mosquito you might think that whole trunk is a single, rigid organ that punctures our skin like a needle and goes directly to our blood vessel and sucks blood out of it trough the same trunk. But actually the inside of the proboscis is much more complex, and contains other mouth parts that female mosquito use to access our blood. One thing to note is that only female mosquitoes have proboscis to bite skin.
Labium is a part of proboscis that covers other mouth parts of a mosquito inside a sheath. The labium is not used for puncturing the skin or sucking blood, and does not even go into the skin. When a mosquito lands on the skin, it uses labium to touch the surface of the skin, so other mouth parts can be inserted into the skin. Inside of the labium there are such mouth parts – 2 mandibles, 2 maxillae, 1 hypopharynx and 1 labrum.
Mandibles and Maxillae
Both pairs of mandibles and maxillae are used to pierce the skin. Mandibles have pointed ends and goes deeper into the skin. Maxillae have flat ends, but they have teeth on the sides that grips to the flash and helps to move other parts deeper inside of the flesh.
Hypopharynx and Labrum
Two important tubes trough what the blood is pumped out of the vessel and saliva is pumped in are called hypopharynx and labrum. Both of these tubes have empty middles, so liquids can be pumped trough them. Hypopharynx is used to pump saliva down and labrum is used to pump blood up from the blood vessel to the mosquito.
How mosquitoes suck blood
A female mosquito is attracted to the human by sensing a carbon dioxide, heat, light and different odors from our skin. When a female mosquito is in a close range to your skin, it finds the area, where blood vessels are closer to the surface of the skin and lands on that area. Sometimes a mosquito can instantly bite trough your skin and start pumping blood from a blood vessel, if it can be easily reached, and other times it can take some time for a mosquito to locate a blood vessel under the skin. If a mosquito doesn’t find a proper place to insert its trunk, it may fly away and look for other places on the skin to locate blood vessels close to skin surface.
When a mosquito female have found a place on your skin, where blood vessels can be easily reached, it inserts proboscis (more precisely mandibles and maxillae) into the skin, so the skin is pierced and mouth parts that does the blood pumping out and saliva pumping in can be inserted into the flash. Saliva that contains substances called anticoagulants is pumped into the flesh trough the Hypopharynx to prevent blood vessel from clotting. Next, mosquito pumps out blood from the blood vessel trough the labrum to the abdomen. Mosquito can suck blood for even up to 4 minutes. Mosquito female will suck blood until it fills the abdomen, or until this process is interfered or mosquito is killed.
After mosquito has finished pumping your blood, the saliva still remains into the area mosquito has bitten and substances from the saliva will cause your body to produce an immune response that causes the swelling and itching feeling around the area. Once the immune system has got rid of substances from saliva, the swelling and the itching of bitten area goes away.