Grylloblattidae, commonly known as the icebugs or ice crawlers, is a family of extremophile (psychrophile) and wingless insects that live in the cold on top of mountains and the edges of glaciers. They are the only living members of Grylloblattodea, which is generally considered an order. Alternatively, Grylloblattodea, along with Mantophasmatodea (rock crawlers), have been ranked as suborders of the order Notoptera. Grylloblattids are wingless insects mostly less than 3 cm long, with a head resembling that of a cockroach, with long antennae and having elongated cerci arising from the tip of their abdomen. They cannot tolerate warmth—most species will die at 10 °C (50 °F)—and many species have small distribution ranges.
Overview Grylloblattids, ice crawlers or icebugs puzzled the scientists who discovered them in 1914, E.M. Walker and T.B. Kurata; the first species named was Grylloblatta campodeiformis, which means "cricket-cockroach shaped like a Campodea" (a kind of two-pronged bristletail). Most are nocturnal and appear to feed on detritus. They have long antennae (23–45 segments) and long cerci (5–8 segments), but no wings. Their eyes are either missing or reduced and they have no ocelli (simple eyes). Their closest living relatives are the recently discovered Mantophasmatodea. Most species are less than 3 cm long, the largest being Namkungia magnus. The family has its own order, Grylloblattodea (sometimes considered a suborder of Notoptera). It contains 5 genera and about 34 extant species. Most species have restricted distributions and small populations and with increased warming their habitats are threatened, making them endangered. In North America some species like Grylloblatta barberi and G. oregonensis are known from single sites.
Habitat and distribution Grylloblattodea are nocturnal extremophiles typically found in leaf litter and under stones in extremely cold environments, usually at higher elevations. They are known to inhabit cold temperate forests to glaciers and the edges of ice sheets. Studies of several North American populations of Grylloblatta have found extremely narrow physiological temperature tolerances, with supercooling points around –4 °C and upper lethal limits near +27 °C, indicating that these insects are specialized for cold. They can be killed at lower temperatures due to ice formation in the body, so when the temperature drops below their optimal range they survive by living under snow pack near the soil. They are very sensitive to heat; many species are killed when the temperature rises about 5 °C above their optimal temperature. They move in response to the seasons so as to maintain an optimal temperature in their foraging habitat. Grylloblattidae are patchily distributed in glaciers, caves, montane environments, and occasionally lower-elevation forests in western North America, East Asia (Korea and Japan), and Central Asia (Siberia, China, and Kazakhstan). They are predicted to occur in several other mountain chains in Asia, including parts of the Himalayas.
Diet Grylloblattids are omnivorous, but feed primarily on dead arthropods and carrion. When arthropod carcasses are scarce, they subsist on plant material.
Evolution Grylloblattidae is generally thought to have emerged from within the "Grylloblattida", a poorly defined group of extinct winged insects that first appeared in the Late Carboniferous, over 300 million years ago. The winged Aristovia from the mid-Cretaceous Burmese amber of Myanmar, around 100 million years ago is thought to be closely related to modern Grylloblattidae due to its very similar mouthparts.
Taxonomy List of Grylloblattodea genera and species along with their type localities:
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