Natural Enemies of Blackflies and Midges
Mermithid Life Cycle
Mermithid Life Cycle:
Mermithid round worms lack a functional digestive tract. Nutrients are consumed from the hemolymph of the host organism and are assimilated across the external epithelium of the infective larva. Eggs hatch to release preinfective larvae. These immatures seek out and invade the host organism. Some parasites are consumed by the host organism and the parasite then burrows throught the GI tract of the host. Other mermithids burrow throught the external cuticle of the host organism.
The infective larvae feeds and grows in the hemocoel of the host. In many black flies and midges, the maturing parasite kills the host larvae and exits through the cuticle. In some individuals or in some host species, the grown parasite does not exit until the host is an adult. In this way, the mermithid can get from location to location, i.e. through the flight of the host.
The newly emerged parasite will live in the new environment for a few days to a few weeks before it molts to the adult stage. This is the non-feeding postinfective larvae.
Finally, the newly molted adults will mate and the females lay eggs. The time period required for this life cycle varies from species to species, but appears to follow an annual cycle with many parasites of black flies and midges.
Mermithid Page
Last modified 13 January 2000