Neodermaptera

Diplatys sp., from here.

Belongs within: Forficulida.
Contains: Anisolabididae, Eudermaptera.

The Neodermaptera are the crown group of the earwigs, dating back to the late Jurassic or early Cretaceous. They are readily distinguished from other living insects by the cerci being modified into a large pair of forceps at the end of the abdomen; they also have the front wings modified into a small pair of hardened veinless tegmina under which the hind wings are folded when not in use. Other characteristic features include the absence of ocelli, three-segmented tarsi, and a reduced ovipositor in females (Grimaldi & Engel 2005).

Wigs and wings and other things
Published 27 October 2010
Arixenia esau, photographed in Deer Cave in Sarawak by Alan Cressler.

The “very interesting, though repulsive, insect” (to use the words of Hebard in 1927) pictured above is a member of today’s subject, the Neodermaptera. Neodermaptera is the clade containing all living members of the Dermaptera, the earwigs, distinguished from various stem groups of the Dermaptera by features such as three-segmented tarsi and the lack of veins in the forewings (Engel 2003). Earwigs are one of the few groups of insects other than beetles to have the forewings hardened into elytriform cases, which in earwigs have also been greatly reduced in size (in earwigs, the hardened forewings are referred to as ‘tegmina’ rather than ‘elytra’, but these seem to be just different words for much the same sort of thing). The rarely-seen hindwings remain folded under the tegmina unless the earwig is flying (which they do not often do) and are simply bizarre. One of the characteristics of polyneopterans, the group of insects including crickets, cockroaches, earwigs and various others, is a tendency towards enlargement of the anal fan, the posterior part of the wing; in earwigs, the anal fan of the hindwing has become enlarged to the point that the wing is almost entirely anal fan with the anterior parts of the wing greatly reduced and crammed into a small toughened section towards the base. One of the stories floating about to supposedly explain the origin of the name ‘earwig’ claims that it is a corruption of ‘ear-wing’. While the wings are indeed ear-shaped, the story rather loses credibility in face of the detail that the average person would probably never see them.

Earwig (probably a female Doru using the key in Engel 2003) with its wings spread, showing the semicircular shape and radiate anal veins. Photo by Sean McCann.

The other distinctive feature of most living earwigs is the development of the cerci at the end of the abdomen into a pair of large, hard forceps. The forceps are used for defense as well as capturing prey in those species that eat animal matter (most earwigs are omnivorous); they may also be used to help fold the wings under the tegmina. In most species, the males have heavier forceps than the females. The only earwigs to have filamentous cerci rather than forceps are the Arixeniidae and Hemimeridae, two families that live in association with mammalian hosts. Arixeniids (such as Arixenia in the top picture) are about 2 cm long and live on bats in south-east Asia; hemimerids are about half that size and live on African giant rats. Not are they distinctive among earwigs, they are the only known quasi-parasitic polyneopterans—I say ‘quasi’-parasitic because they probably feed more on dead skin and host secretions than the actual living host itself. The arixeniids probably feed mostly on the rich deposits of bat poo in host roosting sites. Because of the lack of forceps and other features, these two families have often been placed in separate suborders from the remaining earwigs; at least one author argued that hemimerids should be removed from Dermaptera entirely and treated as a separate order. However, the current consensus is that the two families are probably derived from more normal earwigs, with their distinctive features being adaptations to their symbiotic lifestyles.

Forceps of the recently extinct Labidura herculeana of St Helena, the largest known earwig, alongside a 22 mm specimen of its more average close relative L. riparia. Photo by Philip Ashmole.

Another distinctive feature of the two mammal-associated families is that they are live-bearers. In all other families, the female lays a batch of eggs, usually in a burrow, that she watches over until the young hatch out. She continues to protect her young for their first one or two instars; after that they must fend for themselves. In fact, if the young do not move out quickly enough, their mother will eat them (Rentz & Kevan 1991). Something, perhaps, to be kept in mind by all those parents who feel their adult offspring are taking too long to get their own place.

Systematics of Neodermaptera
<==Neodermaptera [Dermaptoria, Forficulomorpha, Holodermaptera, Labiduroidea]
    |  i. s.: LabidurommaS02
    |--ProtodermapteraGE05
    |    |--KarschiellaRD77 [Karschiellinae, KarschielloideaGE05]
    |    `--Pygidicranidae [Catadermaptera, Pygidicranida, Pygidicranoidea, Pygidiocranidae]GE05
    |         |  i. s.: AraripelabiaS02
    |         |         TagalinaTW05
    |         |         Bormansia Verhoeff 1902NW03
    |         |         Haplodiplatys Hincks 1955NW03
    |         |         Lobodiplatys Kirby 1891NW03
    |         |         Burmapygia resinataGE05
    |         |--Austroblandex [Blandicinae]RK91
    |         |    `--A. bituberculatusRK91
    |         |--EchinosomatinaeNW03
    |         |    |--Echinosoma Audinet-Serville 1839NW03
    |         |    |    `--E. sumatranum (Haan 1842) [=Forficula (Echinosoma) sumatranum; incl. E. westermanni Dohrn 1863]H40
    |         |    `--Archaeosoma Zhang 1994NW03
    |         |         `--*A. serratum Zhang 1994NW03
    |         |--PygidicraninaeRK91
    |         |    |--Cranopygia daemeliRK91
    |         |    |--Dacnodes shortridgeiRK91
    |         |    |--KalocraniaH40
    |         |    |--AcraniaH40
    |         |    `--PygidicranaP92
    |         `--Diplatys Audinet-Serville 1831NW03 [Diplatyidae, DiplatyinaeS02]
    |              |--D. bormansi Burr 1910H40
    |              |--D. gerstaeckeriRD77
    |              |--D. hainanensis Hincks 1940H40
    |              |--D. liberatus Burr 1910H40
    |              |--D. longisetosaA99
    |              `--D. (Syndiplatys) protoflavicollis Sakai & Fujiyama 1989RJ93
    `--Epidermaptera [Anisolabidoidea, Forficuloidea]GE05
         |--+--Apachyidae [Apachyinae, Apachyoidea]GE05
         |  |    |--Dendroiketetes novaeguineaeTW05
         |  |    `--ApachyusGE05
         |  |         |--A. depressusGE05
         |  |         |--A. peterseniC91
         |  |         `--A. queenslandicaZS10
         |  `--Hemimeridae [Dermodermaptera, Diploglossata, Hemimerina, Hemimeroidea, Hemimeromorpha]GE05
         |       |--AreomerusGE05
         |       `--Hemimerus Walker 1871A71
         |            |--*H. talpoides Walker 1871A71
         |            |--H. bouvieriRK91
         |            |--H. morrisiA71
         |            `--H. vosseleriRK91
         `--+--AnisolabididaeGE05
            `--+--EudermapteraGE05
               `--Labiduridae [Labidurinae]GE05
                    |  i. s.: Forcipula decolyi Bormans 1900NW03
                    |         Allosthetus Verhoeff 1903NW03
                    |           `--A. lombokianum Verhoeff 1904NW03
                    |         DoruTW05
                    |           |--D. davisiGE05
                    |           |--D. lineare (Eschscholtz 1822) [=Forficula linearis]R18
                    |           `--D. spiculiferumTW05
                    |--Spondox Burr 1914B14 [PsalinaeH40]
                    |    `--*S. sarasini Burr 1914B14
                    |--Platylabia [Platylabiinae]H40
                    |    `--P. major Dohrn 1867 [incl. P. sparattoides Bormans 1900]H40
                    `--LabidurinaeG70
                         |--Nala lividipesG70
                         `--LabiduraS02
                              |--L. electrinaP92
                              |--L. herculeana [incl. L. loveridgei]S02
                              |--L. riparia (Pallas 1773) [=Forficula riparia]H40
                              |--L. truncataRK91 [=L. riparia truncataM83]
                              `--L. xanthopus [incl. Demogorgon batesi]R15

*Type species of generic name indicated

References

[A71] Askew, R. R. 1971. Parasitic Insects. Heinemann Educational Books: London.

[A99] Ax, P. 1999. Das System der Metazoa II. Ein Lehrbuch der phylogenetischen Systematik. Gustav Fisher Verlag: Stuttgart (translated: 2000. Multicellular Animals: The phylogenetic system of the Metazoa vol. 2. Springer).

[B14] Burr, M. 1914. Les Dermaptères de la Nouvelle-Calédonie et des îles Loyalty. In: Sarasin, F., & J. Roux (eds) Nova Caledonia: Forschungen in Neu-Caledonian und auf den Loyalty-Inseln. A. Zoologie vol. 1 pt 4 pp. 315–324, pl. 9. C. W. Kreidels Verlag: Wiesbaden.

[C91] CSIRO. 1991. The Insects of Australia: A textbook for students and research workers vol. 1. Melbourne University Press: Carlton (Victoria).

Engel, M. S. 2003. The earwigs of Kansas, with a key to genera north of Mexico (Insecta: Dermaptera). Transactions of the Kansas Academy of Science 106 (3–4): 115–123.

[G70] Giles, E. T. 1970. Dermaptera (earwigs). In: CSIRO. The Insects of Australia: A textbook for students and research workers pp. 306–313. Melbourne University Press.

[GE05] Grimaldi, D., & M. S. Engel. 2005. Evolution of the Insects. Cambridge University Press: New York.

Hebard, M. 1927. Studies in Sumatran Dermaptera. Proceedings of the Academy of Natural Sciences of Philadelphia 79: 23–48.

[H40] Hincks, W. D. 1940. Dermaptera (earwigs) from Hainan Island. Notes d’Entomologie Chinoise 8 (2): 29–40.

[M83] Martin, N. A. 1983. Miscellaneous observations on a pasture fauna: an annotated species list. DSIR Entomology Division Report 3: 1–98.

[NW03] Nel, A., A. Waller, V. Albouy, J.-J. Menier & G. de Ploëg. 2003. New fossil earwigs from the lowermost Eocene amber of Paris Basin (France) (Insecta, Dermaptera, family incertae sedis). Geodiversitas 25 (1): 119–129.

[P92] Poinar, G. O., Jr. 1992. Life in Amber. Stanford University Press: Stanford.

[R15] Rehn, J. A. G. 1915. A further contribution to the knowledge of the Orthoptera of Argentina. Proceedings of the Academy of Natural Sciences of Philadelphia 67 (2): 270–292.

[R18] Rehn, J. A. G. 1918. On a collection of Orthoptera from the State of Pará, Brazil. Proceedings of the Academy of Natural Sciences of Philadelphia 70: 144–236, pls 1–2.

[RK91] Rentz, D. C. F., & D. K. McE. Kevan. 1991. Dermaptera (earwigs). In: CSIRO. The Insects of Australia: A textbook for students and research workers vol. 1 pp. 360–368. Melbourne University Press: Carlton (Victoria).

[RD77] Richards, O. W., & R. G. Davies. 1977. Imms’ General Textbook of Entomology 10th ed. vol. 2. Classification and Biology. Chapman and Hall: London.

[RJ93] Ross, A. J., & E. A. Jarzembowski. 1993. Arthropoda (Hexapoda; Insecta). In: Benton, M. J. (ed.) The Fossil Record 2 pp. 363–426. Chapman & Hall: London.

[S02] Shcherbakov, D. E. 2002. Order Forficulida Latreille, 1810. The earwigs and protelytropterans (=Dermaptera DeGeer, 1773 +Protelytroptera Tillyard, 1931). In: Rasnitsyn, A. P., & D. L. J. Quicke (eds) History of Insects pp. 288–291. Kluwer Academic Publishers: Dordrecht.

[TW05] Terry, M. D., & M. F. Whiting. 2005. Mantophasmatodea and phylogeny of the lower neopterous insects. Cladistics 21: 240–257.

[ZS10] Zborowski, P., & R. Storey. 2010. A Field Guide to Insects in Australia 3rd ed. Reed New Holland: Sydney.

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