Caterpillars can look creepy, mostly up close, but as most eat plants, flowers and your favourite shirt, carnivorous classes sound like somewhat out of a horror film. Though, the individuals in the gifs below are undeniably real.
Luckily for those thoughtful they never want to project into the garden again, these creatures are limited to the Hawaiian Landmasses (well fortuitously if you don't live in Hawaii).
The gifs were produced by Robbie Gonzalez at io9 from film released in a BBC biopic. As usual, his write up is bizarre and you should go read it.
The development of this behaviour is a mystery. These are not herbivores that do certain occasional hunting on the side for additional nutrients, like giraffes. Bugs make up their whole diet; when they chew on leaves, they don't even swallow what they've nibbled off. In its place, the caterpillars use the hole they make to anchor themselves for assaults like the ones in the gif.
The caterpillars show aspects of convergent advancement. They exhibit features related with spiders, such as rotating webs to arrest snails. Yet, since Hawaii is well provided with arachnids, it is not recognized why caterpillars accepted a similar ecological niche there and nowhere else, although the nonappearance of some other predators such as praying mantises maybe backed.
Snail catcher's apart, the caterpillars are from the species Eupithecia, common everywhere the world but vegan elsewhere. A minor number of Hawaii's Eupithecia feed on flowers, but since the meat-eating behaviour was revealed in the 1980s nearly 20 species across all Hawaii's islands have been found to involve in it.