An immature stage of an organism which bears no structural resemblence to the mature stage. For example, a maggot is the larva of a fly, a caterpillar is the larva of a moth or butterfly. A caterpillar is just a butterfly maggot . A group of organisms also known as the Roundworms. They have an internal body cavity, with recognisable digestive and reproductive tracts.
Nematodes are generally dioecious .
They reproduce by laying eggs, or larvae which hatch from their eggs inside the body of the female worm. They are among the most common multicellular parasite of humans in the world, although the majority of nematodes are not parasitic, living in the soil. For example, cockroach nymphs can be differentiated from the adults by the fact that the nymphs do not have wings. A parasite which cannot survive or reproduce outside the body of its host organism. For example, one of the dangers for people in the last stages of HIV infection is infection by any number of organisms which pose no threat to individuals with fully functioning immune systems.