Of crustaceans, land-crabs are remarkable for size and number.
Almost all of them are parasitic on other crustaceans.
Small crustaceans and other aquatic animals push their way into the bladders and are unable to escape.
Various species among those that are predaceous attack smaller insects, hunt in packs crustaceans larger than themselves, insert their narrow heads into snail-shells to pick out and devour the occupants, or pursue slugs and earthworms underground.
Wasmann, who has compiled a list of nearly 1 50o species of insects, arachnids and crustaceans, inhabiting ants' nests.