Nematodes, commonly referred to as round worms, live in water, soil and even inhabit humans and animals. There are approximately 15,000 various species of nematodes known and the females are capable of laying over 200,000 eggs, which can be a problem if a female nematode resides inside your body. Distinguishable differences in the physical appearance of the nematodes can help you tell male and female nematodes apart.
Inspect the nematode tails. Males have a slightly bent tail, while the females have a straight tail. The males use the tail during mating.
Look at the nematode's body underneath a microscope. The male nematodes have spicules that lead toward the centre of the body.
Measure the length of an adult female and male nematode. The female nematodes, when fully grown, can grow up to 11 inches, while the males can grow only up to 10 inches. The female nematode's body is also 1/2 inch wider than a male's body.