Embiidina

 Female Antipaluria urichi, photographed by J. Edgerly-Rooks.

Belongs within: Polyneoptera.
Contains: Anisembiidae, Oligotomidae, Embiidae.

The Embioptera, webspinners, are a group of small, retiring insects that construct silken galleries in secluded habitats. Female webspinners are wingless; mature males often have wings, but may lose them after dispersal.

A seclusion of Embioptera
Published 23 November 2007
Webspinner, from Janice Edgerly-Rooks.

A work colleague and I got into a conversation a while ago about collective nouns, and of course that eventually got onto the question of making up appropriate terms for groups of animals that currently lack collective nouns. One suggestion that I came up with that I still rather like the sound of was a “seclusion of embiopterans”. From now on, I urge you to use the term when discussing embiopterans.

If through some bizarre oversight you haven’t regularly found yourself discussing embiopterans, then you really should be. Also known as webspinners or embiids, embiopterans are one of the definite contenders for the total of world’s coolest insects. I have personally come across a specimen in the wild just once that I found clinging to a piece of bark I pulled off its treeunfortunately, I have to admit, no-one around me quite got what I was getting so excited about.

Webspinners are small insects that live in silken galleries they build in secluded areas such as under bark or rocks. There is something of an esoteric contention about what exactly the correct name for the webspinner order should be—Embioptera, Embiidina or Embiodea all can be found. I’m going to stick with Embioptera for no good reason. The name means “lively wings” and is wildly inappropriate—webspinners are not noticeably lively, and more often than not lack wings (females are invariably wingless, males can sometimes be). It has been suggested that the name refers to the flicking movement of the male wings. The wings of male webspinners have large blood sinuses developed from the veins that are pumped full of haemolymph to make the wings rigid when they fly. When the haemolymph is drained from the sinuses, the wings become limp and floppy, able to move in whatever direction is required to let the male crawl through a female’s silk nest, even bending forward over the head if the male goes into reverse.

Webspinners are often referred to as semi-social and females may share inter-connected galleries. Females also show a high level of parental care. However, females will not show any care for the young of others, and social interactions between females should probably be regarded as opportunistic rather than required (Grimaldi & Engel 2005). The female and juvenile webspinners emerge from their silken palaces at night to feed on vegetation and detritus. Adult males, on the other hand, do not feed.

The webspinner’s silk glands are located along the edge of the third segment of the forelimb tarsus, which is noticeable broadened as shown in the diagram above from BugNetMAP. The German name for embiopterans, “tarsenspinner”, is therefore entirely apropos. The stunning “Life in the Undergrowth” series produced by the BBC included spectacular footage of a webspinner constructing its silken fortress, waving its forelimbs in front of itself in a motion that can only be described as “wax on, wax off”. So impermeable is the resulting wall that the spinner must actually cut through it with its mandibles in order to drink from water drops lying on the surface if it is not to dry up completely.

Systematics of Embiidina

Characters (from Rasnitsyn 2002): Size moderate to small. Body elongate. Head large, prognathous, with postoccipital sclerotisation between mouth cavity and occipital foramen, lacking ocelli. Antenna filiform, 12-32-segmented. Mouthparts chewing, male with mandible modified more or less, submentum often shield-like enlarged, sclerotised. Lateral cervicalia divided into 2 pieces. Pronotum lacking paranota. Meso- and metathoraces similarly shaped. Females and many males wingless, nymph-like more or less in thoracic morphology. Wings narrow, homonomous, poor venationally, highly flexible including veins, thus permitting wing to flex over head in backward running in silken tubes. Veins and particularly R surrounded by blood sinus working as vein at flight when filled with blood. Most complete venation with 11 branches only (not counting C) and several weak cross-veins, still more reduced in other representatives. Flight functionally four-winged, in-phase, anteromotoric. Legs short, femora stout (particularly fore and especially so the hind ones), tarsus 3-segmented, fore basitarsus inflated due to silk gland inside. Abdomen cylindrical or, in male, somewhat depressed, 10-segmented, with cercus 2-segmented, male left cercus usually modified and used in copulation. Male genitalia asymmetrical. Ovipositor lost. All stages living in groups in silk tubes spun using fore basitarsal glands under bark, stones, or, in humid climates, externally on substrate, feeding on plant material, mostly dead matter. Female guarding eggs and younger nymphs.

<==Embiidina [Embiaria, Embiida, Embiodea, Embioptera, Euembiaria, Euembioptera, Euplatyptera, Netica, Oligoneura]R07
    |  i. s.: RhagadochirR00
    |         Enveja bequaertiR00
    |         Parthenembia reclusa Ross 1961R00
    |         BerlandembiaR00
    |         Apterembia cercocyrtaR00
    |         Navasiella sulcata [=Oligotoma sulcata]D40
    |         Paedembia Ross 2006 [Paedembiamorpha, Paedembiidae]R06
    |           `--*P. afghanica Ross 2006R06
    |         Idioembia productaRD77
    |--ClothodidaeTW05
    |    |--Chromatoclothoda nanaR00
    |    |--ClothodaR02
    |    |    |--C. longicaudaR00
    |    |    |--C. nobilisR00
    |    |    `--C. urichiRD77
    |    `--AntipaluriaTW05
    |         |--A. caribbeanaR00
    |         |--A. intermediaR00
    |         |--A. marginataR00
    |         `--A. urichiTW05
    `--NeoembiodeaEG06
         |  i. s.: Sorellembia Engel & Grimaldi 2006 [Sorellembiidae]EG06
         |           `--*S. estherae Engel & Grimaldi 2006EG06
         |--+--AndesembiidaeEG06
         |  `--AnisembiidaeEG06
         |--+--OligotomidaeEG06
         |  `--Teratembiidae [Oligembiidae]EG06
         |       |--Teratembia geniculataTW05, R00
         |       |--ParoligembiaR00
         |       |--OligembiaR00
         |       |    |--O. capensisR00
         |       |    |--O. hubbardi [=Oligotoma hubbardi]D40
         |       |    `--O. vetusta Szumik 1994R00
         |       `--DiradiusTW05
         |            |--D. intricatusR00
         |            |--D. plaumanniR00
         |            `--D. vandykeiTW05
         `--+--EmbiidaeEG06
            |--EmbonychaR00 [EmbonychidaeEG06]
            |    `--E. interruptaR00
            |--Burmitembia Cockerell 1919EG06 [BurmitembiidaeR07, Burmitembiinae]
            |    `--*B. venosa Cockerell 1919EG06
            |--Archembiidae [Pachylembiinae, Scelembiinae]EG06
            |    |--Scelembia virgo Ross 1960R00
            |    |--Pachylembia chapalaeR00
            |    |--Embolyntha [=Olyntha (preoc.); Olynthidae]EG06
            |    |    `--E. batesiRD77
            |    `--ArchembiaR00
            |         |--A. batesiR00
            |         |--A. kotzbaueriR00
            |         `--A. lacombeaR00
            `--NotoligotomidaeEG06
                 |  i. s.: Ptilocerembia roepkei Friederichs 1923R63, D40
                 |--NotoligotomaR00 [NotoligotominaeEG06]
                 |    |--N. hardyiR00 [=Oligotoma hardyiD40]
                 |    `--N. nitensR63
                 `--Australembiinae [Australembiidae]EG06
                      |--Australembia Ross 1963R63
                      |    |--*A. incompta Ross 1963R63
                      |    |--A. nodosa (Davis 1944)TW05, R63 [=Metoligotoma nodosaR63]
                      |    `--A. rileyi (Davis 1940) [=Metoligotoma rileyi]R63
                      `--MetoligotomaR00
                           |--M. illawarraeR00
                           |--M. ingensR00
                           |--M. reductaR00
                           |--M. septentrionalisR70
                           `--M. tasmanicaR00

*Type species of generic name indicated

References

[D40] Davis, C. 1940. Taxonomic notes on the order Embioptera. XVIII. The genus Oligotoma Westwood. Proceedings of the Linnean Society of New South Wales 65: 362–387.

[EG06] Engel, M. S., & D. A. Grimaldi. 2006. The earliest webspinners (Insecta, Embiodea). American Museum Novitates 3514: 1–15.

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

[R02] Rasnitsyn, A. P. 2002. Order Embiida Burmeister, 1835. The webspinners (=Embioptera Shipley, 1904). In: Rasnitsyn, A. P., & D. L. J. Quicke (eds) History of Insects pp. 291–293. Kluwer Academic Publishers: Dordrecht.

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

[R63] Ross, E. S. 1963. The families of Australian Embioptera, with descriptions of a new family, genus, and species. Wasmann Journal of Biology 21 (2): 121-136.

[R00] Ross, E. S. 2000. Embia: Contributions to the biosystematics of the insect order Embiidina. Occasional Papers of the California Academy of Sciences 149: 1–53, 1–36.

[R06] Ross, E. S. 2006. Paedembiidae, a remarkable new family and infraorder of Embiidina from Afghanistan. Proceedings of the California Academy of Sciences 57 (27): 785–794.

[R07] Ross, E. S. 2007. The Embiidina of eastern Asia, part I. Proceedings of the California Academy of Sciences, Fourth Series 58 (29): 575–600.

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

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