Mosquitos have their own parasites.
There are flying parasites that suck the blood from mosquitos.
In 1922, a scientist named F.W. Edwards published a paper describing a remarkable thing: a flying, biting midge collected from the Malay Peninsula in southeast Asia that he named Culicoides anophelis. What made the midge was remarkable was the thing it bit: mosquitoes.
Scientific American, Mosquitoes Have Flying, Blood-Sucking Parasites of Their Own, 2014
So those parasites are sucking blood from mosquitos.
Today we know that female mosquitos need blood for their eggs:
Typically, both male and female mosquitoes feed on nectar and plant juices, but in many species the mouthparts of the females are adapted for piercing the skin of animal hosts and sucking their blood as ectoparasites. In many species, the female needs to obtain nutrients from a blood meal before it can produce eggs, whereas in many other species, it can produce more eggs after a blood meal. A mosquito has a variety of ways of finding its prey, including chemical, visual, and heat sensors. Both plant materials and blood are useful sources of energy in the form of sugars, and blood also supplies more concentrated nutrients, such as lipids, but the most important function of blood meals is to obtain proteins as materials for egg production.
Wikipedia, Mosquito, 2018
So those parasites are actually sucking blood from female mosquitos.
However 1400 years ago the Quran said that
mosquitos had their own parasites:
Quran 2.26 Allah does not shy away from making an example of a mosquito and what is above it. As for those who believe, they know that it is the Truth from their Lord. But as for those who disbelieve, they say, "What did Allah intend by this example?" He leads astray many thereby, and He guides many thereby; but He misleads thereby only the evildoers.
"Mosquito and what is above it" this is a parasite on a mosquito. Bauda in Arabic " بعوضة " is female mosquito. So the Quran is referring to female mosquito that has parasite.
How could an illiterate man who lived 1400 years ago have known that female mosquitos have parasites?