Zoraptera

The insect order Zoraptera, commonly known as angel insects, contains small and soft bodied insects with two forms: winged with wings sheddable as in termites, dark and with eyes (compound) and ocelli (simple); or wingless, pale and without eyes or ocelli. They have a characteristic nine-segmented beaded (moniliform) antenna. They have mouthparts adapted for chewing and are mostly found under bark, in dry wood or in leaf litter.[1]

Winged fossil of Zorotypus hirsutus from the Late Cretaceous (Cenomanian) aged Burmese amber, around 99 million years old

Zoraptera
Temporal range:
Zorotypus from Los Bancos, Pichincha, Ecuador
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Branch: Metapterygota
Infraclass: Neoptera
Cohort: Polyneoptera
Order: Zoraptera
Silvestri, 1913
Families
Diversity
51 species

Description
Zorotypus sp.

The name Zoraptera, given by Filippo Silvestri in 1913,[2] is misnamed and potentially misleading: "zor" is Greek for pure and "aptera" means wingless. "Pure wingless" clearly does not fit the winged alate forms, which were discovered several years after the wingless forms had been described.

The members of this order are small insects, 3 millimetres (0.12 in) or less in length, that resemble termites in appearance and in their gregarious behavior. They are short and swollen in appearance. They belong to the hemimetabolous insects. They possess mandibulated biting mouthparts, short cerci (usually 1 segment only), and short antennae with 9 segments. The abdomen is segmented in 11 sections.[3] The maxillary palps have five segments, labial palps three, in both the most distal segment is enlarged. They have six Malpighian tubules, and their abdominal ganglia have fused into two separate ganglionic complexes.[4] Immature nymphs resemble small adults. Each species shows polymorphism. Most individuals are the apterous form or "morph", with no wings, no eyes, and no or little pigmentation. A few females and even fewer males are in the alate form with relatively large membranous wings that can be shed at a basal fracture line. Alates also have compound eyes and ocelli, and more pigmentation. This polymorphism can be observed already as two forms of nymphs. Wingspan can be up to 7 millimetres (0.28 in), and the wings can be shed spontaneously. When observed, wings have simple venation.[3] Under good conditions the blind and wingless form predominates, but if their surroundings become too tough, they produce offspring which develop into winged adults with eyes. The wings are paddle shaped, and have reduced venation.

Systematics

Phylogeny

The phylogenetic relationship of the order remains controversial and elusive. At present the best supported position based on morphological traits recognizes the Zoraptera as polyneopterous insects related to the webspinners of the order Embioptera. However, molecular analysis of 18s ribosomal DNA supports a close relationship with the superorder Dictyoptera.[5][6][7][8][9] There are eleven extinct species known as of 2017, many of the fossil species are known from Burmese amber.[10]

Classification

The Zoraptera are currently divided into two families, four subfamilies, nine genera and a total of 51 species, some of which have not been yet described.[11][12][13]

  • Family Zorotypidae Silvestri, 1913, stat. revid. Kočárek, Horká & Kundrata, 2020
    • Subfamily Zorotypinae Silvestri, 1913
      • Zorotypus Silvestri, 1913, stat. revid. Kočárek, Horká & Kundrata, 2020 — 7 spp.
      • Usazoros Kukalova-Peck & Peck, 1993 stat. restit. Kočárek, Horká & Kundrata, 2020 — 1 sp.
    • Subfamily Spermozorinae Kočárek, Horká & Kundrata, 2020
      • Spermozoros Kočárel, Horká & Kundrata, 2020 — 6 spp.
  • Family Spiralizoridae Kočárek, Horká & Kundrata, 2020
    • Subfamily Latinozorinae Kočárek, Horká & Kundrata, 2020
      • Latinozoros Kukalova-Peck & Peck, 1993, stat. restit. Kočárek, Horká & Kundrata, 2020 — 3 spp.
    • Subfamily Spiralizorinae Kočárek, Horká & Kundrata, 2020
      • Spiralizoros Kočárek, Horká & Kundrata, 2020 — 12 spp.
      • Centrozoros Kukalova-Peck & Peck, 1993 stat. restit. Kočárek, Horká & Kundrata, 2020 (=Meridozoros Kukalova-Peck & Peck, 1993; Floridazoros Kukalova-Peck & Peck, 1993) — 8 spp.
      • Cordezoros Kočárek, Horká & Kundrata, 2020 — 1 sp.
      • Scapulizoros Kočárek, Horká & Kundrata, 2020 — 1 sp.
      • Brazilozoros Kukalova-Peck & Peck, 1993 stat. restit. Kočárek, Horká & Kundrata, 2020 — 3 spp.

Incertae sedis

The following nine species are considered Zoraptera incertae sedis:[11]

  • Zorotypus congensis van Ryn Tournel, 1971
  • Zorotypus javanicus Silvestri, 1913
  • Zorotypus juninensis Engel, 2000
  • Zorotypus leleupi Weidner, 1976
  • Zorotypus longicercatus Caudell, 1927
  • Zorotypus newi (Chao & Chen, 2000) Engel & Grimaldi, 2000 (=Formosozoros newi Chao & Chen, 2000)
  • Zorotypus sechellensis Zompro, 2005
  • Zorotypus swezeyi Caudell, 1922

Extinct taxa
  • †Xenozorotypus Engel & Grimaldi 2002

Behavior and ecology

Zorapterans live in small colonies beneath rotting wood, lacking in mouthparts able to tunnel into wood, but feeding on fungal spores and detritus. These insects can also hunt smaller arthropods like mites and collembolans.[14]

Centrozoros gurneyi lives in colonies which range in size from a few dozen to several hundred individuals, but most often number about 30 individuals. The males are slightly larger than the females, and they fight for dominance.[15]

When two colonies of Usazoros hubbardi are brought together experimentally, there is no difference in behavior towards members of the new colony. Therefore, colonies in the wild might merge easily. Winged forms are rare. The males in most colonies establish a linear dominance hierarchy in which age or duration of colony membership is the prime factor determining dominance. Males appearing later in colonies are at the bottom of the hierarchy, regardless of their body size. By continually attacking other males, the dominant male monopolizes a harem of females. The members of this harem stay clumped together. There is a high correlation between rank and reproductive success of the males.[16][17]

Latinozoros barberi lack such a dominance structure but display complex courtship behavior including nuptial feeding. The males possess a cephalic gland that opens in the middle of their head. During courtship they secrete a fluid from this gland and offer it to the female. Acceptance of this droplet by the female acts as behavioral releaser and immediately leads to copulation.[14]

In Spermozoros impolitus, copulation does not occur, but fertilization is accomplished instead by transfer of a spermatophore from the male to the female. This 0.1-millimetre (0.0039 in) spermatophore contains a single giant sperm cell, which unravels to about the same length as the female herself, 3 millimetres (0.12 in). It is thought that this large sperm cell prevents fertilization by other males, by physically blocking the female's genital tract.[18][19]

Effects on ecosystem

Zoraptera are thought to provide some important services to ecosystems. By consuming detritus, such as dead arthropods, they assist in decomposition and nutrient cycling.[20]

References
  1. Rafael, JA; Godoi, FDP; Engel, MS (2008). "A new species of Zorotypus from eastern Amazonia, Brazil (Zoraptera: Zorotypidae)". Transactions of the Kansas Academy of Science. 111 (3 & 4): 193–202. doi:10.1660/0022-8443-111.3.193. S2CID 85821812.
  2. Silvestri, F (1913). "Descrizione di un nuovo ordine di insetti". Bol. Lab. Zool. Gen. Agric. Portici. 7: 193–209.
  3. Gullan; Granston (2005). The Insects: An Outline of Entomology.
  4. Evolution of attachment structures in the highly diverse Acercaria (Hexapoda)
  5. Yoshizawa (2007). "The Zoraptera problem: evidence for Zoraptera + Embiodea from the wing base" (PDF). Systematic Entomology. 32 (2): 197–204. doi:10.1111/j.1365-3113.2007.00379.x. hdl:2115/33766. S2CID 53321436.
  6. Yoshizawa, K; Johnson, KP (2005). "Aligned 18S for Zoraptera (Insecta): Phylogenetic position and molecular evolution". Molecular Phylogenetics and Evolution. 37 (2): 572–580. doi:10.1016/j.ympev.2005.05.008. hdl:2115/43133. PMID 16005647.
  7. Engel, MS; Grimaldi, DA (2002). "The first mesozoic Zoraptera (Insecta)". American Museum Novitates (3362): 1–20. CiteSeerX 10.1.1.571.3443. doi:10.1206/0003-0082(2002)362<0001:tfmzi>2.0.co;2. S2CID 54764188.
  8. Ishiwata, K; Sasaki, G; Ogawa, J; Miyata, T; Su, Z-H (2011). "Phylogenetic relationships among insect orders based on three nuclear protein-coding gene sequences". Molecular Phylogenetics and Evolution. 58 (2): 169–180. doi:10.1016/j.ympev.2010.11.001. PMID 21075208.
  9. Wang, X.; Engel, M.S.; Rafael, J.A.; Dang, K.; Wu, H.; Wang, Y.; Xie, Q.; Bu, W. (2013). "A unique box in 28S rRNA is shared by the enigmatic insect order Zoraptera and Dictyoptera". PLOS ONE. 8 (1): e53679. Bibcode:2013PLoSO...853679W. doi:10.1371/journal.pone.0053679. PMC 3536744. PMID 23301099.
  10. Yin, Ziwei; Cai, Chenyang; Huang, Diying (2018). "New zorapterans (Zoraptera) from Burmese amber suggest higher paleodiversity of the order in tropical forests". Cretaceous Research. 84: 168–172. doi:10.1016/j.cretres.2017.11.028.
  11. Kočárek, Petr; Horká, Ivona; Kundrata, Robin (12 January 2020). "Molecular Phylogeny and Infraordinal Classification of Zoraptera (Insecta)". Insects. 11 (51): 1–28. doi:10.3390/insects11010051.
  12. Zoraptera Species File (Version 5.0/5.0; retrieved 29 May 2021)
  13. "Order Zoraptera Silvestri 1913". The Paleobiology Database. Retrieved 26 November 2020.
  14. Choe, Jae C. (1997). "The evolution of mating systems in the Zoraptera: mating variations and sexual conflicts". In Choe, Jae C.; Crespi, Bernard J. (eds.). The Evolution of Mating Systems in Insects and Arachnids. Cambridge: Cambridge University Press. pp. 130–145. doi:10.1017/cbo9780511721946.008. ISBN 978-0-511-72194-6.
  15. The Other Insect Societies
  16. Choe, Jae C. (1994). "Sexual selection and mating system in Zorotypus gurneyi Choe (Insecta: Zoraptera)" (PDF). Behavioral Ecology and Sociobiology, II. Determinants and Dynamics of Dominance. 34 (4): 233–237. doi:10.1007/bf00183473. hdl:2027.42/46900. ISSN 0340-5443. S2CID 42298642.
  17. Choel, Jae C. (1994). "Sexual selection and mating system in Zorotypus gurneyi Choe (Insecta : Zoraptera), I. Dominance hierarchy and mating success". Behavioral Ecology and Sociobiology. 34 (2): 87–93. doi:10.1007/bf00164179. hdl:2027.42/46900. ISSN 0340-5443. S2CID 9112078.
  18. Dallai, R.; et al. (12 May 2013). "Divergent mating patterns and a unique mode of external sperm transfer in Zoraptera: an enigmatic group of pterygote insects". Naturwissenschaften. 100 (6): 581–594. Bibcode:2013NW....100..581D. doi:10.1007/s00114-013-1055-0. ISSN 0028-1042. PMID 23666111. S2CID 16363067.
  19. "The tiny insect with the massive sperm". New Scientist. No. 2919. 1 June 2013. p. 17.
  20. Engel, Michael (2007). "The Zorotypidae of Fiji (Zoraptera)" (PDF). Bishop Museum Occasional Papers.

General references
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