In the last decade, new methods of estimating global species richness have been developed and existing ones improved through the use of more appropriate statistical tools and new data. Taking the mean of most of these new estimates indicates that globally there are approximately 1.5 million, 5.5 million, and 7 million species of beetles, insects, and terrestrial arthropods, respectively. Previous estimates of 30 million species or more based on the host specificity of insects to plants now seem extremely unlikely. With 1 million insect species named, this suggests that 80% remain to be discovered and that a greater focus should be placed on less-studied taxa such as many families of Coleoptera, Diptera, and Hymenoptera and on poorly sampled parts of the world. DNA tools have revealed many new species in taxonomically intractable groups, but unbiased studies of previously well-researched insect faunas indicate that 1–2% of species may be truly cryptic.


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Literature Cited

  1. Adis J. 1.  1990. Thirty million arthropod species—too many or too few?. J. Trop. Ecol. 6:115–18 [Google Scholar]
  2. Agnarsson I, Coddington JA, Kuntner M. 2.  2013. Systematics: progress in the study of spider diversity and evolution. Spider Research in the 21st Century: Trends and Perspectives D Penney 58–111 Manchester, UK: Siri Sci. Press [Google Scholar]
  3. Barrowclough GF, Cracraft J, Klicka J, Zink RM. 3.  2016. How many kinds of birds are there and why does it matter?. PLOS ONE 11:e0166307 [Google Scholar]
  4. Basset Y, Samuelson GA, Allison A, Miller SE. 4.  1996. How many species of host-specific insects feed on a species of tropical tree?. Biol. J. Linn. Soc. 59:201–16 [Google Scholar]
  5. Bebber DP, Marriott FHC, Gaston KJ, Harris SA, Scotland RW. 5.  2007. Predicting unknown species numbers using discovery curves. Proc. R. Soc. B 274:1651–58 [Google Scholar]
  6. Bickford D, Lohman DJ, Sodhi NS, Ng PK, Meier R. 6.  et al. 2007. Cryptic species as a window on diversity and conservation. Trends Ecol. Evol. 22:148–55 [Google Scholar]
  7. Burns JM, Janzen DH, Hajibabaei M, Hallwachs W, Hebert PDN. 7.  2008. DNA barcodes and cryptic species of skipper butterflies in the genus Perichares in Area de Conservacion Guanacaste, Costa Rica. PNAS 105:6350–55 [Google Scholar]
  8. Caley MJ, Fisher R, Mengersen K. 8.  2014. Global species richness estimates have not converged. Trends Ecol. Evol. 29:187–88 [Google Scholar]
  9. Costello MJ, May RM, Stork NE. 9.  2013. Can we name Earth's species before they go extinct?. Science 339:413–16 [Google Scholar]
  10. Costello MJ, Wilson S, Houlding B. 10.  2012. Predicting total global species richness using rates of species description and estimates of taxonomic effort. Syst. Biol. 61:871–83 [Google Scholar]
  11. Dolphin K, Quicke DL. 11.  2001. Estimating the global species richness of an incompletely described taxon: an example using parasitoid wasps (Hymenoptera: Braconidae). Biol. J. Linn. Soc. 73:279–86 [Google Scholar]
  12. Duff A, Lott DA, Buckland PC. 12.  2012. Checklist of Beetles of the British Isles Iver, UK: Pemberley Books [Google Scholar]
  13. Erwin TL. 13.  1982. Tropical forests: their richness in Coleoptera and other arthropod species. Coleopterists Bull 36:74–75 [Google Scholar]
  14. Erwin TL. 14.  1988. The tropical forest canopy. Biodiversity EO Wilson, FM Peter 123–29 Washington, DC: Natl. Res. Council [Google Scholar]
  15. Gaston KJ. 15.  1991. Body size and probability of description: the beetle fauna of Britain. Ecol. Entomol. 16:505–8 [Google Scholar]
  16. Gaston KJ. 16.  1991. The magnitude of global insect species richness. Conserv. Biol. 5:283–96 [Google Scholar]
  17. Gaston KJ, Gauld ID. 17.  1993. How many species of pimplines (Hymenoptera: Ichneumonidae) are there in Costa Rica?. J. Trop. Ecol. 9:49199 [Google Scholar]
  18. Gaston KJ, Mound LM. 18.  1993. Taxonomy, hypothesis testing and the biodiversity crisis. Proc. R. Soc. B 251:139–142 [Google Scholar]
  19. Halliday R, O'Connor B, Baker A. 19.  2000. Global diversity of mites. See Ref. 47 192–203
  20. Hamilton AJ, Basset Y, Benke KK, Grimbacher PS, Miller SE. 20.  et al. 2010. Quantifying uncertainty in estimation of global arthropod species richness. Am. Nat. 176:90–95 [Google Scholar]
  21. Hamilton AJ, Basset Y, Benke KK, Grimbacher PS, Miller SE. 21.  et al. 2010. Quantifying uncertainty in estimation of tropical arthropod species richness. Am. Nat. 176:90–95 Erratum. 2011 Am. Nat. 177:544–5 [Google Scholar]
  22. Hamilton AJ, Novotný V, Waters EK, Basset Y, Benke KK. 22.  et al. 2013. Estimating global arthropod species richness: refining probabilistic models using probability bounds analysis. Oecologia 171:357–65 [Google Scholar]
  23. Hammond PM. 23.  1992. Species inventory. Global Biodiversity: Status of the Earth's Living Resources: A Report B Groombridge 17–39 London: Chapman and Hall [Google Scholar]
  24. Hammond PM. 24.  1995. The current magnitude of biodiversity. Global Biodiversity Assessment VH Heywood 113–38 Cambridge, UK: Cambridge Univ. Press [Google Scholar]
  25. Hebert PDN, Penton EH, Burns JM, Janzen DH, Hallwachs W. 25.  2004. Ten species in one: DNA barcoding reveals cryptic species in the neotropical skipper butterfly Astraptes fulgerator. PNAS 101:14812–17 [Google Scholar]
  26. Hendrich L, Morinière J, Haszprunar G, Hebert PD, Hausmann A. 26.  et al. 2015. A comprehensive DNA barcode database for Central European beetles with a focus on Germany: adding more than 3500 identified species to BOLD. Mol. Ecol. Resour. 15:795–818 [Google Scholar]
  27. Hodkinson ID, Casson D. 27.  1991. A lesser predilection for bugs: Hemiptera (Insecta) diversity in tropical forests. Biol. J. Linn. Soc. 43:101–9 [Google Scholar]
  28. Janzen DH, Hallwachs W, Blandin P, Burns JM, Cadiou J-M. 28.  et al. 2009. Integration of DNA barcoding into an ongoing inventory of complex tropical biodiversity. Mol. Ecol. Resour. 9:1–26 [Google Scholar]
  29. Ji Y, Ashton L, Pedley SM, Edwards DP, Tang Y. 29.  et al. 2013. Reliable, verifiable and efficient monitoring of biodiversity via metabarcoding. Ecol. Lett. 16:1245–57 [Google Scholar]
  30. Joppa LN, Roberts DL, Myers N, Pimm SL. 29a.  2011. Biodiversity hotspots house most undiscovered plant species. PNAS 108:13171–76 [Google Scholar]
  31. Joppa LN, Roberts DL, Pimm SL. 30.  2011. How many species of flowering plants are there?. Proc. R. Soc. B 278:554–59 [Google Scholar]
  32. Kirby W, Spence W. 31.  1826. An Introduction to Entomology, or Elements of the Natural History of Insects London: Longman, Rees, Orme, Brown and Green [Google Scholar]
  33. Linnaeus C. 32.  1753. Species Plantarum: 167 Holmiae, Swed.: Impensis Laurentii Salvii [Google Scholar]
  34. Marske KA, Ivie MA. 33.  2003. Beetle fauna of the United States and Canada. Coleopt. Bull. 57:495–503 [Google Scholar]
  35. May RM. 34.  1986. How many species are there?. Nature 324:514–15 [Google Scholar]
  36. May RM. 35.  1988. How many species are there on Earth?. Science 241:1441–49 [Google Scholar]
  37. May RM. 36.  1990. How many species?. Philos. Trans. R. Soc. B 330:293–304 [Google Scholar]
  38. May RM. 37.  2000. The dimensions of life on Earth. See Ref. 47 30–45
  39. 38. Millen. Ecosyst. Assess. 2005. Current State and Trends Washington, DC: Millen. Ecosyst. Assess. [Google Scholar]
  40. Mora C, Tittensor DP, Adl S, Simpson AGB, Worm B. 39.  2011. How many species are there on Earth and in the ocean?. PLOS Biol 9:e1001127 [Google Scholar]
  41. Nielsen ES, Mound LA. 40.  2000. Global diversity of insects: the problems of estimating numbers. See Ref. 47 213–21
  42. Novotný V, Basset Y. 41.  2000. Rare species in communities of tropical insect herbivores: pondering the mystery of singletons. Oikos 89:564–72 [Google Scholar]
  43. Novotný V, Basset Y, Miller SE, Weiblen GD, Bremer B. 42.  et al. 2002. Low host specificity of herbivorous insects in a tropical forest. Nature 416:841–44 [Google Scholar]
  44. Ødegaard F. 43.  2000. How many species of arthropods? Erwin's estimate revisited. Biol. J. Linn. Soc. 71:583–97 [Google Scholar]
  45. Pimm SL, Jenkins CN, Joppa LN, Roberts DL, Russell GJ. 44.  2010. How many endangered species remain to be discovered in Brazil. Nat. Conserv. 8:71–77 [Google Scholar]
  46. Pimm SL, Raven P, Peterson A, Şekercioğlu ÇH, Ehrlich PR. 45.  2006. Human impacts on the rates of recent, present, and future bird extinctions. PNAS 103:10941–46 [Google Scholar]
  47. Raven PH. 46.  1985. Disappearing species. a global tragedy. Futurist 19:8–14 [Google Scholar]
  48. Raven PH. 47.  2000. Nature and Human Society: The Quest for a Sustainable World Washington, DC: Natl. Acad. Press [Google Scholar]
  49. Raven PH, Yeates DK. 48.  2007. Australian biodiversity: threats for the present, opportunities for the future. Aust. J. Entomol. 46:177–87 [Google Scholar]
  50. Ray J. 49.  1714. The Wisdom of God Manifested in the Works of the Creation London, UK: William Innys, 6th ed.. [Google Scholar]
  51. Rouhan G, Gaudeul M. 50.  2014. Plant taxonomy: a historical perspective, current challenges, and perspectives. Molecular Plant Taxonomy1–37 New York: Springer [Google Scholar]
  52. Sabrosky CW. 51.  1953. How many insects are there?. Syst. Zool. 2:31–36 [Google Scholar]
  53. Scheffers BR, Joppa LN, Pimm SL, Laurance WF. 52.  2012. What we know and don't know about Earth's missing biodiversity. Trends Ecol. Evol. 27:501–10 [Google Scholar]
  54. Schmidt S, Schmid‐Egger C, Morinière J, Haszprunar G, Hebert PD. 53.  2015. DNA barcoding largely supports 250 years of classical taxonomy: identifications for Central European bees (Hymenoptera, Apoidea partim). Mol. Ecol. Resour. 15:985–1000 [Google Scholar]
  55. Soberón J, Llorente J. 54.  1993. The use of species accumulation functions for the prediction of species richness. Conserv. Biol. 7:480–88 [Google Scholar]
  56. Stork NE. 55.  1988. Insect diversity—facts, fiction and speculation. Biol. J. Linn. Soc. 35:321–37 [Google Scholar]
  57. Stork NE. 56.  1993. How many species are there?. Biodivers. Conserv. 2:215–32 [Google Scholar]
  58. Stork NE. 57.  1997. Measuring global biodiversity and its decline. Biodiversity II: Understanding and Protecting Our Biological Resources ML Reaka-Kudla, DE Wilson, EO Wilson 41–68 Washington, DC: Joseph Henry Press [Google Scholar]
  59. Stork NE. 58.  1999. Estimating the number of species on Earth. The Other 99%: The Conservation and Biodiversity of Invertebrates W Ponder, D Lunney 1–7 Chipping Norton, Aust: R. Zool. Soc. New S. Wales [Google Scholar]
  60. Stork NE. 59.  1999. The magnitude of biodiversity and its decline. The Living Planet in Crisis: Biodiversity Science and Policy J Cracraft, FT Grifo 3–32 New York: Columbia Univ. Press [Google Scholar]
  61. Stork NE, Gaston KJ. 60.  1990. Counting species one by one. New Sci 1729:43–47 [Google Scholar]
  62. Stork NE, McBroom J, Gely C, Hamilton AJ. 61.  2015. New approaches narrow global species estimates for beetles, insects, and terrestrial arthropods. PNAS 112:7519–23 [Google Scholar]
  63. Walter DE. 62.  2001. Achilles and the mite: Zeno's paradox and rainforest mite diversity. Acarology: Proceedings of the 10th International Congress, 2001113–20 Sydney, Aust.: CSIRO Publ. [Google Scholar]
  64. Wilson SP, Costello MJ. 63.  2005. Predicting future discoveries of European marine species by using a non-homogeneous renewal process. J. R. Stat. Soc. C 54:897–918 [Google Scholar]
  65. Zhang Z-Q. 64.  2011. Animal Biodiversity: An Outline of Higher-Level Classification and Survey of Taxonomic Richness Auckland, N. Z.: Magnolia Press [Google Scholar]

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