Apterygota

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Apterygota
Temporal range: Devonian–Recent
[1]
Petrobius maritimus
(Archaeognatha: Machilidae)
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Subclass: Apterygota
Orders

The Apterygota are a small subclass of primitive insects.

They are insects which have never had wings at any time in their evolutionary history. Their first known occurrence in the fossil record is in the Rhynie chert of the Devonian period, ~400 million years ago. While some other insects, such as fleas, also lack wings, these are descended from winged insects, and have lost them during the course of evolution. By contrast, the apterygotes are a primitive group of insects that diverged from other orders before wings evolved.

They have some other primitive traits (features). The nymphs (younger stages) go through little or no metamorphosis, so they look like the adults. They continue to moult throughout life, with multiple instars (stages) after reaching sexual maturity. All other insects have only a single sexually mature adult stage. Their skin is thin, making them appear translucent. Males deposit sperm packages rather than fertilising the female internally.[2]

Currently, no species are listed as being at conservation risk.

History of the group[change | change source]

The classification of the Apterygota changed over time. By the mid 20th century, the subclass included four orders (Collembola, Protura, Diplura, and Thysanura). With the advent of a more rigorous cladistic methodology, the subclass turned out to be paraphyletic. The first three groups formed a monophyletic group, the Entognatha. The Thysanura is more closely related to winged insects.[3] thus rendering even the amyocerate apterygotes paraphyletic.

Some think the Collembola are no longer insects at all, but their position is not yet clear.[4][5][6][7][8]

Sources[change | change source]

  1. Hoell, H.V., Doyen, J.T. & Purcell, A.H. (1998). Introduction to Insect Biology and Diversity, 2nd ed.. Oxford University Press. p. 320. ISBN 0-19-510033-6 .
  2. Hoell, H.V., Doyen J.T. & Purcell A.H. (1998). Introduction to insect biology and diversity. 2nd ed, Oxford University Press. pp. 333–340. ISBN 0-19-510033-6 .
  3. Orders – Thysanura & Archaeognatha
  4. Frédéric Delsuc, Matthew J. Phillips & David Penny (2003). "Comment on Hexapod origins: monophyletic or paraphyletic?" (PDF). Science 301 (5639): 1482. doi:10.1126/science.1086558 . PMID 12970547 . http://www.sciencemag.org/cgi/reprint/301/5639/1482d.pdf.
  5. Francesco Nardi, Giacomo Spinsanti, Jeffrey L. Boore, Antonio Carapelli, Romano Dallai & Francesco Frati (2003). "Hexapod origins: monophyletic or paraphyletic?". Science 299 (5614): 1887–1889. doi:10.1126/science.1078607 . PMID 12649480 .
  6. Francesco Nardi, Giacomo Spinsanti, Jeffrey L. Boore, Antonio Carapelli, Romano Dallai & Francesco Frati (2003). "Response to comment on Hexapod origins: monophyletic or paraphyletic?" (PDF). Science 301 (5639): 1482. doi:10.1126/science.1087632 . http://www.sciencemag.org/cgi/reprint/301/5639/1482e.pdf.
  7. Yan Gao, Yun Bu & Yun-Xia Luan (2008). "Phylogenetic relationships of basal hexapods reconstructed from nearly complete 18S and 28S rRNA gene sequences" (PDF). Zoological Science 25 (11): 1139–1145. doi:10.2108/zsj.25.1139 . PMID 19267625 . http://decapoda.nhm.org/pdfs/31595/31595.pdf.
  8. Alexandre Hassanin (2006). "Phylogeny of Arthropoda inferred from mitochondrial sequences: strategies for limiting the misleading effects of multiple changes in pattern and rates of substitution" (PDF). Molecular Phylogenetics and Evolution 38 (1): 100–116. doi:10.1016/j.ympev.2005.09.012 . PMID 16290034 . http://www.csulb.edu/~dlunderw/entomology/Arthropodphylogeny2006.pdf.


  • Firefly Encyclopedia of Insects and Spiders, edited by Christopher O'Toole, ISBN 1-55297-612-2, 2002