Classification And Features Of The Order

The Grylloblattodea comprise a single family, Grylloblattidae, which includes only four genera. Grylloblatta occurs in North America and Canada, where at least 11 species are known. Grylloblattina is known from a few species from Siberia. Grylloblattella has species known from Korea, Japan, and Siberia. Galloisiana contains at least 10 species from Japan. The group, however, is undoubtedly larger, since new species are discovered every few years.

FIGURE 1 Copulating pair of grylloblattids, G. nipponensis: the female is the lower individual (note ovipositor); the male has the eversible sac of the left phallomere exposed. [From Nagashima et al. In Ando, H. (ed.). (1982). "Biology of the Notoptera," p. 48, Kashiyo-Insatu, Nagano, Japan.]

FIGURE 1 Copulating pair of grylloblattids, G. nipponensis: the female is the lower individual (note ovipositor); the male has the eversible sac of the left phallomere exposed. [From Nagashima et al. In Ando, H. (ed.). (1982). "Biology of the Notoptera," p. 48, Kashiyo-Insatu, Nagano, Japan.]

Grylloblattids are cryptic, ground-dwelling insects that prefer wet habitats and cool temperatures. They shun light and occur under stones or in dense leaf litter. Species of Grylloblatta that live under rocks under or near snowbanks emerge after dark and feed as scavengers or predators on dead or dying insects that have been blown onto the snow from lower elevations. During winter, the species probably occupy the airspace between the ground and overlying snowpack, where they remain active at temperatures of 0°C. Massive fat bodies build up prior to winter; during winter, the insects may feed on decaying plant material. Korean species live under debris on the floor of caves at only 200 m altitude and apparently never venture forth from the cave habitat. The most widespread species in Japan, Galloisiana nipponensis, is found at elevations ranging from 300 to 3000 m, where the insects live under stones and in the leaf litter of thick, mixed coniferous and hardwood forests. These species consume both insects and plant material day and night.

The resemblance of grylloblattids to Dermaptera has been shown to be superficial and is associated only with the fact that both have a projecting head. The head, however, is typical of orthopteroid insects. The antennae are elongate and thin. The mouthparts are structured like those of a predator. Ocelli are absent, and the eye comprises fewer ommatidia in young instars than in adults. The legs are simple, slender, and not suited for jumping. The abdomen comprises 11 segments, with the cerci long and flexible and the male genitalia asymmetrical. The ovipositor comprises three pairs of slender, tapering, partly free valves.

Although grylloblattids are normally considered to be cool-adapted insects, they cannot withstand temperatures much below 0°C. At -5.5 to 8.0°C they stress. Contrary to the popular belief that they can withstand very low temperatures, they can be killed by ice formation within the body as a result of their low levels of glycerol, sorbitol, or erythrol.

Copulation has been observed in a few species. In G. nipponensis, the female is chased and seized by the male. The resulting copulation can last from 30 min to 4 h. Males always assume a position on the right side of the female as a response to the male's asymmetrical genitalia. Oviposition occurs 10 to 50 days after copulation. Females lay eggs with the elongate ovipositor in wood or under stones and decaying plant material. None have been found in moss. Oviposition for each egg takes about 3 min, and females lay 5 or 6 eggs per day to a total of about 30 eggs. A captive female laid 145 eggs in her lifetime. The large, black eggs, develop over periods of from 5 months to 3 years.

See Also the Following Articles

Blattodea • Orthoptera • Phasmida

Further Reading

Ando, H. (ed.). (1982). "Biology of the Notoptera." Kashiyo-Insatsu, Nagano, Japan.

Storozhenko, S. (1989). A review of the family Gryllop(b)lattidae (Insecta). Articulata 13, 167-181.

Joseph S. Elkinton

University of Massachusetts

The gypsy moth, Lymantria dispar, is one of the world's most damaging defoliators of hardwood forest trees. It is native to Europe and Asia. It was introduced from Europe to North America near Boston, Massachusetts, in 1869 and has been spreading slowly south and west ever since. A large body of research has focused on the biology, management, and population dynamics of this species.

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