Little hijacked ant,
blade held in jagged pincers,
awaits her demise.
The lancet liver fluke is a parasite of devious means. As an adult it lives in the livers of ruminant animals, often cattle, but it has an ingenious method of getting from one liver to another. First, its eggs are excreted in its host’s faeces, which is then consumed by a snail. The larvae develop into juveniles in the snail’s digestive tract and are eventually themselves excreted.
This is where the ants come in. Ants use snail slime for moisture and so consume the juveniles. Once inside an ant the parasites cause it to climb a blade of grass and clamp its mandibles to the top. The ant will remain attached all night and then return to its normal behaviour during the day. The aim of the parasite is for the ant (and attached blade of grass) to be eaten by a grazing animal – the parasite is then back in its main host and the cycle starts again. Summarised in Tarry, 1969.