Phylogeny And Distribution Of Dermaptera

Early in the 20th century, Burr established suborders of the Dermaptera recognized by most contemporary systematists. The four suborders (three of them recent) are as follows:

1. Archidermaptera, represented by 10 fossil specimens from the Jurassic; they are characterized by unsegmented cerci and tarsi having four or five segments.

2. Forficulina, the suborder containing most earwigs (i.e., 1800 described species, in 180 genera); cerci are unsegmented (except in a few primitive larvae) and forcepslike.

3. Hemimerina, composed of 10 species in one genus; they have filiform (segmented) cerci, and are wingless, blind, viviparous (pseudoplacental) ectoparasites of African rats.

4. Arixenina, composed of five species in two genera; like the Hemimerina, they are viviparous (pseudoplacental), wingless, blind, and ectoparasitic of vertebrates. The Arixenina live on bats in Malayan—Philippine region; Popham considered this group to be a sister group of the Labiidae.

Popham based his phylogeny of families on the structure of the male genitalia (Fig. 3). The Hemimerina consists only of

FIGURE 3 Phylogeny of the families of the Dermaptera. [Amended figure reprinted with the permission of Cambridge University Press from Popham, E. (1965). The functional morphology of reproductive organs of the common earwig (Forficula auricularia) and other Dermaptera with reference to the natural classification of the order. J. Zool. 146, 1—43.]

FIGURE 3 Phylogeny of the families of the Dermaptera. [Amended figure reprinted with the permission of Cambridge University Press from Popham, E. (1965). The functional morphology of reproductive organs of the common earwig (Forficula auricularia) and other Dermaptera with reference to the natural classification of the order. J. Zool. 146, 1—43.]

the family Hemimerinidae. The Pygidicranidae are frequently regarded as the most primitive family of earwigs, in as much as the males have two functional penis lobes. The Carcino-phoridae also show less specialized, ancestral traits (and are typically treated as wingless, though some are fully winged). The Arixinidae and Labiidae are treated as sister groups (though this is not generally accepted). The Chelisochidae and Forficulidae are the most specialized families (i.e., display the most derived traits). The Forficulidae are considered to be "higher earwigs" (more recently derived) because the males have a single functional penis lobe. This family is the best-represented family in North America.

The current geographical distribution of most families of earwigs was largely determined by continental drift, with two main centers of radiation before the Triassic opening of the Pacific ocean being the equatorial region of the eastern Pacific (Pygidicranidae, Carcinophoridae, Arixinidae, and Labiidae) and the Afro-Indian circumtropical center (Labiduridae, Chelosochidae, and Forficulidae).

The distribution has also been largely affected by climatic conditions: earwigs were "discouraged" from spreading northward from the tropics by mountain ranges of southern Europe and Asia; only more specialized members have become established in the Palearctic region (and none have been reported in the polar regions). Although most earwigs have wings, they seldom fly. The cosmopolitan distribution of some species can be attributed to their habit of hiding in crevices, especially in timber or other material that is transported by commerce.

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