Phylogeny and Classification

Paleontology, comparative morphology, and molecular studies suggest that the sister group of the Orthoptera is the Phasmida (see Flook et al., 1999). Quite possibly, the earliest orthopterans, belonging to the suborder Ensifera, evolved from phasmidlike ancestors early in the Carboniferous period. The early evolution of the Orthoptera led toward the specialization of the fore wings as tegmina, the development of stridulatory and tympanal organs, and the enlargement of the hind femora to accommodate the muscles for jumping (Carpenter, 1992). Even by the Upper Carboniferous period, there was a clear separation of the two major evolutionary lines, one of which led to the Ensifera (crickets, long-horned grasshoppers, etc.) and the other to the Caelifera (short-horned grasshoppers and their allies). This led to the suggestion that the two groups evolved independently from different protorthopteran ancestors (Ragge, 1955; Sharov, 1968; Hennig, 1981). Thus, some authorities, for example, Vickery et al. (1974) and Kevan (1986), have argued strongly that each group be given ordinal status, the ensiferans being placed in the order Grylloptera, with the caeliferans in the order Orthoptera sensu stricto. Most studies, including recent cladistic and molecular analyses, favor the view that the differences between each group do not warrant their separation into two orders and that the traditional subdivision of the Orthoptera into the suborders Ensifera and Caelifera be retained. The possible evolutionary relationships of the major families of Orthoptera are indicated in Figure 7.17.

Within the Ensifera, the Grylloidea may be the sister group to the other three super-families. Of these, the Hagloidea is an almost entirely fossil group, containing only four living species.

The Caelifera may be arranged in six superfamilies, with the Tridactyloidea being the sister group to the remaining five. Both the tridactyloids and the Tetrigoidea show a number of primitive characters that place them near the base of the caeliferan stem, and they feed on bacteria, algae, mosses, or roots of higher plants. By contrast, the generally grasshopperlike members of the remaining superfamilies (in older classifications collectively called the Acridomorpha [Dirsch, 1975]) feed on the foliage of higher plants.

Suborder Ensifera

Members of the suborder Ensifera are characterized by their multisegmented antennae that, with few exceptions, are as long as or longer than the body. Tympanal organs, when present, are located on the fore tibiae. The principal living superfamilies are the Gryllacridoidea (Stenopelmatoidea), Tettigonioidea, and Grylloidea.

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