Family Mermithidae

                                 Revised 01/28/26

Classification:

Phylum Nematoda

  Class Enoplea

• A family of nematode parasites mainly of insects.
• Obligate parasites of invertebrates
• Nematodes of the family Mermithidae are lethal parasites of arthropods, mainly insects.
• Their hosts include species of at least 15 different orders of insects (Nickle 1972).
• Descriptions of many species are not satisfactory and many described species are considered as species inquirendae because the adult nematodes have not been found and, in many cases, need to be obtained by laboratory rearing of emerged postparasitic juveniles.
• Mermithids emerge as later-stage juveniles or as adults from the insect host. Adults mate and lay eggs or release juveniles into the benthic soil at the bottom of a shallow water body
• In some species, eggs are a resistant life stage that can be transported and distributed for biological control putposes (Petersen, 1985; Platzer, 2007).
• Molecular methods are aiding understanding of the taxonomy of the family (Gradinarov, 2014).

Biology:

Density-dependent sex determination of the parasitic nematodes is a general feature of mermithid life history.  Parasitism of the host by multiple nematode individuals (termed superparasitism) reults in a higher proportion of the infective juveniles developing into males and, consequently, proportionally fewer females .  Additionally, superparasitism reduces availability of host resources per parasite and the proprtionally fewer and smaller nematode females may be less fecund (Blackmore and Charnov, 1989; Christie, 1929; Mullens and Luhring, 2023; Petersen, 1972; Sanad et al., 2013).

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References

Blackmore, M. S. and Charnov, E. L. 1989. Adaptive variation in environmental sex determination in a nematode. American Naturalist 134:817-823. Christie, J. R. 1929. Some observations on sex in the Mermithidae. Journal of Experimental Zoology 53:59-76.

Christie, J.R. 1929. Some observations on sex in the Mermithidae. Journal of Experimental Zoology 53:59-76

Gradinarov, D. 2014. The mermithid species Isomermis lairdi (Nematoda, Mermithidae), previously only known in Africa, found in Europe. Zookeys 454:1-11.

Mullens, B.A. and Luhring, K.A. 2023. Parasite load effects on sex ratio, size, survival and mating fitness of Heleidomermis magnapapula in Culicoides sonorensis. J. Nematology 55: e2023-1 r | DOI: 10.2478/jofnem-2023-0052

Nickle WR. 1972. A contribution to our knowledge of the Mermithidae (Nematoda). Journal of Nematology 4: 113-146. 

Petersen, J. J. 1972. Factors affecting the sex ratio of mermithid parasites of mosquitoes. Journal of Nematology 4:83-87.

Petersen, J.J. 1985. Nematodes as biological control agents: Part 1. Mermithidae. Advances in Parasitology 24:307-346.

Platzer, E.G. 2007. Mermithid nematodes. Journal of the American Mosquito Control Association Bulletin 7:58-64

Sanad, M., Shamseldin, M. M., Elgindi, A. Y. and Gaugler, R. 2013. Host penetration and emergence patterns of the mosquito-parasitic mermithids Romanomermis iyengari and Strelkovimermis spiculatus (Nematoda: Mermithidae). Journal of Nematology 45:30-37

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