Rockcrawlers are wingless, and slender, with flattened bodies 15 to 30 mm (0.6 to 1.2 in) long. The antennae are long, and there are two cerci, short, antennalike projections at the tail end of the body. Between the cerci in the female is a swordlike ovipositor, or egg depositor, which she uses to place her eggs in the soil. The three pairs of legs are spaced widely along the body, and the tarsi, or feet, have five segments. Rockcrawlers have biting mouthparts and either two small eyes or none at all. The North American species are dark brown, black, yellow-brown, or grayish.
Grylloblattids live at freezing temperatures most of the year and take two years to mature. They develop by incomplete metamorphosis, hatching from the egg as nymphs, or miniature adults, and grow through a series of stages, or instars, each separated by a shedding of the skin. Grylloblattids are active at -2.5? to 11.3? C (27.5? to 52.3? F). Temperatures above 20.5? C (68.9? F) are fatal, and the insects will die if held only briefly in a human hand. They eat other small invertebrates that live in or around the ice and snow or that are blown there by accident. Grylloblattids will also eat dead insects or sometimes plants and moss.
Scientific classification: Grylloblattids make up the order Grylloblattodea in the class Insecta, phylum Arthropoda.