Grylloblattodea

(Rock-crawlers)

Class Insecta

Order Grylloblattodea

Number of families 1

Evolution and systematics

About 300 species of fossil Grylloblattodea are known from the late Carboniferous to the early Cretaceous and were among the most abundant and diverse insects during the Permian. The order Grylloblattodea is considered ancestral to all other related orders (stoneflies, webspinners, and earwigs). There is only one living family, Grylloblattidae, which belongs to the suborder Grylloblattina.

Physical characteristics

The extant family Grylloblattidae is characterized by an elongate, subcylindrical, slightly flattened body. The head is short and prognathous, with small or absent eyes. The antennae are filiform, with 28–50 segments. All three thoracic segments are similar—more or less flattened. The legs are similar in appearance, with five segmented tarsi, and are adapted for running. Wings are entirely absent. The abdomen has 10 segments, and the cerci are long, with seven to 12 segments. The female has a long ovipositor consisting of six valves. The asymmetrical genitalia of the male are located in the ninth abdominal segment. Adult rock-crawlers range from 0.6 to 1.4 in (15–35 mm) in length. Adults are brown, with light brown legs and ventral surface of the abdomen. Nymphs are ivory white or yellowish; sometimes a completely black (melanistic) form occurs.

Distribution

The extant family Grylloblattidae includes five genera and 27 species from Siberia, northeastern China, Korea, Japan, United States, and Canada.

Habitat

Modern rock-crawlers live on and in soil, in caves, beneath stones, and in crevices of mountainous regions. Grilloblattidae also occur in mixed forests and near the snowfields at elevations of 656–10,499 ft (200–3,200 m). Rock-crawlers are adapted to cool-temperate habitats. For example, the optimum temperature for Grylloblatta campodeiformis is 38.7°F (3.7°C) to 59.9°F (15.5°C). Individuals increase activity until death occurs at 82°F (27.8°C). Cooling from 38.7°F (3.7°C) to 21.9°F (−5.6°C) results in decreased activity; prostration and death occur at 20.8°F (−6.2°C).

Behavior

Ice-crawlers typically are found singly or in sexual pairs. Occasionally, the female may suddenly eat the male. Individual populations occupy areas from 984 ft (300 m) to approximately 3,280 ft (1 km) in diameter. Rock-crawlers avoid light and are nocturnal. Because they are small, wingless insects, grylloblattids are limited in their migratory movements. They may be able to migrate for a few hundred meters at most; in general, populations occupy areas from 984 to 3,280 ft (300–1,000 m) in diameter.

Feeding ecology and diet

Both adults and nymphs are carnivorous and consume the soft tissues of insects and spiders. The nymphs also eat parts of plants or other organic matter in the soil. Grylloblattids first detect prey with their maxillae and bite them with their mandibles. The North American Grylloblatta moves at night to the surface of the snow to forage. Nymphs can be active without food for three to six months.

Reproductive biology

Courtship and mating of grylloblattids take place under stones. The male and female face each other, touching each other with their antennae. The male chases the female and grasps her right hind leg or cercus with his mandibles. He then seizes the posterior edge of the female's prothorax with his mandibles. The male mounts the female and twists his abdomen underneath hers to copulate. Owing to the asymmetry of the male external genitalia, the male always positions himself to the right of the female during copulation. Copulation lasts from about 30 minutes to four hours. In Galloisiana nipponensis, oviposition (the laying of eggs) occurs 10–50 days after copulation, throughout the year. The females lay 60–150 eggs in or on the soil, under stones and fallen leaves, or in decayed wood. The eggs are black and oval and measure 0.06–0.1 in (1.6–2.5 mm) in length. The first instar nymph hatches about 150 days after oviposition, at 50–53.6°F (10–12°C). Viable eggs may remain dormant from one to three years. There are eight or so nymphal instars, three during the first year, the next four at one-year intervals, and the last about six weeks after the preceding one. Both nymphs and adults are observed throughout the year.

Conservation status

No species of grylloblattids are listed by the IUCN.

Significance to humans

Rock-crawlers are important objects of study in terms of the physiological adaptation of insects to low temperatures and in the study of Pleistocene zoogeography.

Species accounts

List of Species

Japanese rock-crawler

Galloisiana nipponensis

family

Grylloblattidae

taxonomy

Galloisia nipponensis Caudell and King, 1924, Chuzenji near Nikko, Honshu, Japan.

other common names

None known.

physical characteristics

Body length of adult is 0.73–.0.87 in (18.5–22 mm).

distribution

Numerous local populations throughout Honshu and Shikoku, Japan.

habitat

This species lives in mixed forests near mountain streams at elevations of 656–3,281 ft (200–1,000 m) but sometimes occupies limestone caves.

behavior

Nocturnal. Typically found singly or in sexual pairs.

feeding ecology and diet

Carnivorous. Nymphs also eat plant parts.

reproductive biology

After copulation, females lay 60–150 black eggs, which hatch after about 150 days.

conservation status

Not listed by IUCN.

significance to humans

Studied because of their adaptation to low temperatures.

Northern rock-crawler

Grylloblatta campodeiformis

family

Grylloblattidae

taxonomy

Grylloblatta campodeiformis Walker, 1914, Sulphur Mountain, Banff, Canada.

other common names

French: Grylloblatte du nord.

physical characteristics

Body length of adult is 0.98–1.06 in (25–27 mm).

distribution

Divided into three subspecies. G. c. campodeiformis is known from southeastern British Columbia and southwestern Alberta, Canada, and northern Idaho, western Washington, and western and southern Montana in the United States. G. c. athapaska is distributed in southwestern British Columbia and G. c. nahanni in northeastern British Columbia.

habitat

This species usually is found near the timberline on mountains, along the margins of glacial bogs, and buried up to 3.3 ft (1 m) in rock scree.

behavior

Nocturnal and negatively phototropic. Moves at night to snow surface for foraging.

feeding ecology and diet

Scavenges dead insects and spiders.

reproductive biology

The total cycle has been calculated to take about seven years.

conservation status

Not listed by IUCN.

significance to humans

Important for scientific study for its adaptation to surviving at low temperatures. This species is also the emblem of the Entomological Society of Canada.

Pravdin's rock-crawler

Grylloblattella pravdini

family

Grylloblattidae

taxonomy

Galloisiana pravdini Storozhenko and Oliger, 1984, Teletskoe Lake, Altai, Russia.

other common names

None known.

physical characteristics

Body length of adult is 0.64–0.69 in (16.3–17.5 mm).

distribution

The Altai mountains of Russia.

habitat

This species is found beneath stones in mixed forest at elevations of 1,312–2,297 ft (400–700 m).

behavior

Not known.

feeding ecology and diet

Not known.

reproductive biology

Not known.

conservation status

Not listed by IUCN.

significance to humans

None known.

Djakonov's rock-crawler

Grylloblattina djakonovi

family

Grylloblattidae

taxonomy

Grylloblattina djakonovi Bey-Bienko, 1951, Petrov Island, Primorye, Russia. Two subspecies are recognized.

other common names

None known.

physical characteristics

Body length of adult is 0.77–0.89 in (19.5–22.5 mm).

distribution

Southwestern part of the Sikhote-Alin mountain range and the northwestern part of the Chanbaishan mountains, Russia. The two subspecies are found on opposite sides of the Partizanskaya River: G. d. djakonovi is distributed in the Partizanskii Range eastward to the Partizanskaya River, and G. d. kurentzovi is found in the Livadiiskii Range westward to the Partizanskaya River.

habitat

Usually at elevations of 656–3,281 ft (200–1,000 m), but the population from Petrov Island occurs under stones in mixed forest at about 32.8–65.6 ft (10–20 m) from the seaside.

behavior

Nocturnal. Typically found singly or in sexual pairs.

feeding ecology and diet

Carnivorous. Nymphs also eat plant parts.

reproductive biology

After copulation, females lay 60–150 black eggs, which hatch after about 150 days.

conservation status

Not listed by IUCN.

significance to humans

None known.

Biryong rock-crawler

Namkungia biryongensis

family

Grylloblattidae

taxonomy

Namkungia biryongensis Namkung, 1974, Yongtanri, Jeongseonmyeon, Gangwon Province, Korea.

other common names

Korean: Biryong-galleuwa beolle.

physical characteristics

The largest living species of rock-crawler, with an adult body length of 1.34–1.38 in (34–35 mm).

distribution

Gangwon Province of Korea, 311 mi (500 km) northeast of Seoul.

habitat

This species is found under gravel about 65.6–98.4 ft (20–30 m) inside the entrances of the limestone caves Biryong donggul and Baekryeong dong-gul.

behavior

Not known.

feeding ecology and diet

Not known.

reproductive biology

Not known.

conservation status

Not listed by IUCN.

significance to humans

None known.

Resources

Books

Ando, H., and T. Nagashima. "A Preliminary Note on the Embryogenesis of Galloisiana nipponensis (Caudell et King)." In Biology of the Notoptera, edited by Hiroshi Ando. Nagano, Japan: Kashiyo-Insatsu, 1982.

Nagashima, T., H. Ando, and G. Fukushma. "Life History of Galloisiana nipponensis (Caudell et King)." In Biology of the Notoptera, edited by Hiroshi Ando. Nagano, Japan: Kashiyo-Insatsu, 1982.

Rentz, D. C. F. "A Review of the Systematics, Distribution and Bionomics of the North American Grylloblattidae." In Biology of the Notoptera, edited by Hiroshi Ando. Nagano, Japan: Kashiyo-Insatsu, 1982.

Storozhenko, S. Y. "Fossil History and Phylogeny of Orthopteroid Insects." In The Bionomics of Grasshoppers, Katydids, and Their Kin, edited by S. K. Gangwere, M. C. Muralirangan, and Meera Muralirangan. New York: Cambridge University Press, 1997.

——. Systematics, Phylogeny and Evolution of the Grylloblattidan Insects (Insecta: Grylloblattida). Valdivostok, Russia: Dalnauka, 1998. (In Russian.)

——. "Order Grylloblattida Walker, 1914." In History of Insects, edited by A. P. Rasnitsyn, D. L. J. Quicke. Boston: Kluwer Academic Publishers, 2002.

Vickery, V. R., and D. K. M. Kevan. A Monograph of the Orthopteroid Insects of Canada and Adjacent Regions. Vol. 1. Ste. Anne de Bellevue, Canada: Lyman Entomological Museum and Research Laboratory, 1983.

Visscher, S. N., M. Francis, P. Martinson., and S. Baril. "Laboratory Studies on Grylloblatta campodeiformis Walker." In Biology of the Notoptera, edited by Hiroshi Ando. Nagano, Japan: Kashiyo-Insatsu, 1982.

Periodicals

Rasnitsyn, A. P. "Grylloblattide Are the Living Members of the Order Protoblattodea (Insecta)." Doklady Biological Sciences 228 (1976): 273–275.

Storozhenko, S. Y., and J. K. Park. "A New Genus of the Ice Crawlers (Grylloblattida: Grylloblattidae) from Korea." Far Eastern Entomologist 114 (2002): 18–20.

Vrsansky, P., S Y. Storozhenko, C. C. Labandeira, and P. Ihringova. "Galloisiana olgae sp. nov. (Grylloblattodea: Grylloblattidae) and the Paleobiology of a Relict Order of Insects." Annals of the Entomological Society of America 94, no. 2 (2001): 179–184.

S. Y. Storozhenko