When a water mite – one of the 2mm big ones – is spotted in the microscope, you will see up to several mites at once.
There are both male and female water mites. The fertilized female mite finds an insect larva (or, in the lack of a better host, a human), which she latches onto and then injects the mouth parts into the skin. After a few hours her abdomen swells up and she is sought out by one or more males. The males then spend the rest of their short lives to crawling on large abdomen of the fertilized female. When they get hungry, they inject their mouth parts into the female and suck out nourishment. In the female’s abdomen, the next generation of water mites is developed.
You can clearly see the new mites because the female abdomen is completely transparent. The water mites are born as adults. Often the males help giving birth to the new mites. They cut a hole in the abdomen with their powerful hind legs and pull out the new females for immediate mating. Males only help at the birth of female mites. New males are on their own.