Morphology
''Paragordius varius'' have a slightly off-center mouth and distinct grooves running along its cylindrical body. Male worms can grow to be 12–29 cm in length whereas females are generally longer and can grow to be 12–31 cm in length. This parasite is aLife cycle and reproduction
The life cycle of ''P. varius'' includes a terrestrial and an aquatic stage. Adult worms emerge from their insect hosts late spring or summer. They swim in the shallow waters in search for a mate. Upon encounter, the female signals to the male that she is ready and willing to mate. No penetration occurs during copulation and the male releases his sperm immediately. However, if the sperm does not land on the appropriate posterior area of the female, conception will fail. Once the sperm lands, a large circular glob forms which passes into the seminal receptacle of the female within twenty four hours of mating. Upon conception, the female ''P. varius'' lays a long, white, string of eggs and dies. Up to as six million eggs are produced by a single female. Eggs are released into the water where they hatch into larvae. The larvae infect larvae of aquatic insects and snails that serve as paratenic hosts. In these theyDevelopment
The life cycle of nematomorphs has 4 stages: First is the egg, which takes about 10–12 days to complete its larval development after being laid. Second is the pre-parasitic larva that hatches from the egg; the fully developed larva remains in the egg 7–10 days before hatching. Third is the parasitic larva that develops within an invertebrate host; larvae swim about freely in the water after hatching, and are ingested with water when insects drink. If the larvae does not find a host within a few days, they will die. The larvae uses hooks on the anterior portions of the body to infect its host. Once inside a host insect, the larva penetrate the insect's gut and enter its body cavity and forms a cyst in the muscular or intestine region. They mature and escape from the host in two to three months. When the intermediate host completes metamorphosis it comes across a definitive host and evolves into an adult. The final stage of the nematomorphs is the free-living aquatic adult; the development only takes about thirty days where the ''P. varius'' is able to produce three generations in one year. They break through the body wall of the host and become free-living. Eventually the ''P. varius'' will leave the definitive host when the host is near water. This is done by manipulating its host to migrate to a shallow body of water.Host species
This parasite is known to infect insect species in the order orthoptera. Amongst the host species are grasshoppers, crickets, cockroaches, snails, mosquito larvae, or other small aquatic animals and insects. Mammals are not capable of being infected. However, dogs, cats, and even humans have been known to swallow adult worms accidentally.Host manipulation
Like many horsehair worms, ''P. varius'' can alter its host's behaviour. It does this at least in two distinct ways. In the definitive cricket (''Distribution
''Paragordius varius'' has been found all across North and South America ranging as far north as Canada and as far south as Argentina. It prefers environments containing bodies of water needed for reproduction. ''P. varius'' has also been found to be able to withstand temperatures as cold as -70 °C. It can be frozen at this temperature for weeks and when it thaws out, it is still completely capable of infecting its next host. This species prefers lakes over streams.References
{{Taxonbar, from=Q3821528 Nematomorpha Parasitic protostomes Parasites of insects Suicide-inducing parasitism Animals described in 1851