Spinochordodes tellinii and paragordius tricuspidatus species achieve this by causing grasshopper and crickets to jump into waterbodies drowning themselves when the horsehair worm reaches its adult stage. This leads to the most famous trait of some species of horsehair worms, the ability to highjack the terrestrial host’s nervous system, altering their behaviour to make them actively seek out water. The horsehair worm needs to ensure the host is near water before emerging as an adult.

This process rarely kills the host as the parasite relies on the host’s nutrients. It may take a couple of weeks to months to complete the parasitic stage. The larvae feed on nutrients inside the host absorbing them directly through their skin and moulting as they grow. Once inside the host the larvae live inside the primary body cavity. Some larvae have a sharp spike-like appendage on their anterior end that acts as a needle that penetrates host tissues. Marine species in the genus Nectonema specialise in parasitising crustacean hosts underwater. The intermediate hosts act as transportation from aquatic areas to their terrestrial hosts. Outside the UK, other species specialise in parasitising terrestrial hosts such as mantids by first being consumed by mosquitos or mayflies. Some species such as Spinochordodes tellinii and Paragordius tricuspidatus infest hosts such as grasshoppers or crickets that feed on vegetation with larvae attached. They are then eaten alongside vegetation or drunk with water by a suitable host which varies between species.

When the eggs hatch, the larvae can encyst to survive until they are ingested.

In the larval stage, these worms must find an arthropod host to complete their life cycle, often killing the host, making them obligate parasitoids.Įggs are laid in sticky strings underwater or on nearby vegetation depending on the species.

AboutHorsehair worms’ adults are free-living in aquatic freshwater or marine environments and capable of moving across damp terrestrial areas.

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