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Rock-Crawlers: Grylloblattodea

ROCK-CRAWLERS: Grylloblattodea

NORTHERN ROCK-CRAWLER (Grylloblatta campodeiformis): SPECIES ACCOUNT

PHYSICAL CHARACTERISTICS

Rock-crawlers are slender, flattened, soft-bodied insects. Adults range from 0.6 to 1.4 inches (15 to 35 millimeters) in length. They are mostly brown, while the legs and underside are light brown. The larvae (LAR-vee), or young, form of the animal, which must go through changes in form before becoming an adult, are white, yellowish, or sometimes black. The head is short, with small compound eyes present or absent, depending on species. Their chewing mouthparts point forward. The antennae (an-TEH-nee), or sense organs, are threadlike and made up of twenty-eight to fifty segments. Rock-crawlers never have wings, and all of their legs are long and thin. The abdomen has ten segments, with a pair of long, segmented structures at the tip.

GEOGRAPHIC RANGE

All twenty-seven species of rock-crawlers live in the Northern Hemisphere; they are found in Siberia, northeastern China, Korea, and Japan. Eleven species are known to live in the United States and Canada.

HABITAT

Rock-crawlers are secretive animals that live at elevations between 656 and 10,499 feet (between 200 and 3,200 meters) in mixed forests or in mountains above the highest point where trees can grow, usually near snowfields. They prefer cooler temperatures, of about 38.7°F to 60°F (3.7°C to 15.5°C), and are found in moist habitats beneath rocks and in crevices (KREH-vuh-ses) in rocky snowfields or inside subterranean lava tubes.

DIET

Both adults and young eat the soft tissues of captured and dead insects and spiders. The larvae also eat parts of plants and other bits of plant or animal tissues in the soil.

BEHAVIOR AND REPRODUCTION

Rock-crawlers are typically found singly or in sexual pairs and are active at night.

Some North American species look for food on the surface of the snow. They detect prey and other food items with their mouthparts. The larvae can survive without food for three to six months. Although they are adapted for survival at cooler temperatures, rock-crawlers will die if they are caught in extended periods of freezing temperatures. They will also die if temperatures rise to 82°F (28°C).

Courtship takes place under stones and includes lots of leg nibbling and touching with the antennae. Occasionally, the female may suddenly eat the male. Females lay sixty to 150 eggs in or on the soil, in decayed wood, or under leaves and stones. The eggs hatch in about 150 days but may take as long as three years. The larvae strongly resemble the adults when they hatch and gradually get larger as they mature. They molt, or shed their outer covering, or exoskeleton, three times during the first year and once a year for the next four or more years before reaching adulthood.

ONE OF NATURE'S CHIMERAS

In Greek mythology the Chimera (ki-MER-a) was a fire-breathing monster, part lion, part goat, and part snake. When first discovered high in the mountains of Canada in 1914, rock-crawlers were recognized as the chimeras of the insect world. The first-known species, Grylloblatta campodeiformis, was named after three other kinds of insects: crickets, cockroaches, and diplurans. It was not until 1932 that these puzzling animals were placed in their very own order, the Grylloblattodea.

ROCK-CRAWLERS AND PEOPLE

Rock-crawlers are important research animals for scientists studying how animals survive in cold temperatures. The distribution of rock-crawlers may also provide clues about where ancient animals lived during the Ice Ages over the past two million years.

CONSERVATION STATUS

Only one species of rock-crawler is listed by the World Conservation Union (IUCN). The Mount Saint Helens rock-crawler is listed as Vulnerable, or facing a high risk of extinction in the wild. It is found in the U.S. Pacific Northwest.

NORTHERN ROCK-CRAWLER (Grylloblatta campodeiformis): SPECIES ACCOUNT

Physical characteristics: The adults measure 0.98 to 1.06 inches (25 to 27 millimeters) in length. Their bodies are yellowish brown. The antennae have fewer than thirty segments.


Geographic range: Northern rock-crawlers are found in southeastern British Columbia, southwestern Alberta, eastern Washington, northern Idaho, western and southern Montana.


Habitat: Northern rock-crawlers live in the mountains above the highest point where trees can grow. They prefer habitats where there is plenty of moisture and the temperatures range between 38°F and 60°F (3°C and 15°C), such as the edges of glacial bogs in moss, decaying wood, or damp areas deep under rocks. They are sometimes buried up to 3.3 feet (1 meter) in piles of pebbles, small stones, and other rocky debris.

Diet: Adults find and eat mostly small, dead insects, especially wingless crane flies. The larvae scavenge dead insects but also feed on some plant tissues.


Behavior and reproduction: Northern rock-crawlers live alone or in pairs. They avoid light and forage for food at night on and around snowfields. Although they prefer to live at cooler temperatures, they will die if exposed to long periods of freezing temperatures. The larvae may take up to seven years to reach adulthood.

Northern rock-crawlers and people: This insect is an important research animal for scientists studying how organisms survive at low temperatures. They are used as the official symbol of a scientific organization that studies insects, the Entomological Society of Canada, as well as of the Department of Entomology at Montana State University in Bozeman.


Conservation status: This species is not endangered or threatened. ∎

FOR MORE INFORMATION

Books:

Tavoloacci, J., ed. Insects and Spiders of the World. New York: Marshall Cavendish, 2003.

Web sites:

"Grylloblattodea." Tree of Life Web Project. http://tolweb.org/tree?group=Grylloblattidae&contgroup=Neoptera (accessed on October 25, 2004).

"Ice Bugs (Grylloblattodea)." Gordon's Insect World. http://www.earthlife.net/insects/gryllobl.html (accessed on September 14, 2004).

Meyer, John R. "Grylloblattodea." http://www.cals.ncsu.edu/course/ent425/compendium/rockcrwl.html#pix (accessed on October 25, 2004).

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