Chordodes Formosanus

Short answer: Chordodes formosanus is a horsehair worm (phylum Nematomorpha) first described in 2011 by Ming-Chung Chiu and colleagues from specimens taken from Hierodula mantises in Taiwan and Japan. Later surveys found it in other mantises and in long-horned grasshoppers too.

Horsehair worms live as adults in water. Females lay strings of eggs there, and the larvae infect aquatic insect larvae and form cysts inside them. When those insects grow up and fly to land, a mantis or cricket that eats one picks up the cyst. The worm then grows inside the host's body cavity until it fills much of the abdomen. When it's mature, the infected host heads for water, and the worm emerges and swims off to mate. Researchers have long linked this water-seeking behavior to the parasite, but exactly how it works is still being studied. A 2023 Current Biology study of the related species Chordodes fukuii found more than 1,400 worm genes that closely match mantis genes, evidence of horizontal gene transfer. Many of those genes became more active during manipulation, which suggests they may help the worm influence its host. Adult horsehair worms of different species range from a few centimeters to over 2 m long, though most are 20 to 40 cm. The specimens measured in the 2011 description of C. formosanus were about 7 to 28 cm. The footage shows a green mantis held over and then in a glass of water as a long dark worm emerges from its abdomen.