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Insect biodiversity accounts for a large proportion of all biodiversity on the planet—over half of the estimated 1.5 million organism species described are classified as insects.

Number of species

Estimates of the total number of insect species or those within specific orders are often highly variable. Globally, averages of these predictions estimate there are around 1.5 million beetle species and 5.5 million insect species with around 1 million insect species currently found and described.

Between 950,000–1,000,000 of all described species are insects, so over 50% of all described eukaryotes (1.8 million) are insects (see illustration). With only 950,000 known non-insects, if the actual number of insects is 5.5 million, they may represent over 80% of the total, and with only about 20,000 new species of all organisms being described each year, most insect species likely will remain undescribed, unless species descriptions greatly increase in rate. Of the 24 orders of insects, four dominate in terms of numbers of described species, with at least 670,000 species included in Coleoptera, Diptera, Hymenoptera and Lepidoptera.

As of 2017, at least 66 insect species extinctions had been recorded in the previous 500 years, which generally occurred on oceanic islands. Declines in insect abundance have been attributed to artificial lighting, land use changes such as urbanization or agricultural use, pesticide use, and invasive species. Some studies have suggested a large proportion of insect species are threatened with extinction in the 21st century, though ecologist Manu Sanders notes that many of these findings are often biased by excluding data that shows increases or stability in diversity, and limited to specific geographic areas and specific groups of species. Claims of pending mass insect extinctions or "insect apocalypse" based on a subset of these studies have been popularized in news reports, but often make claims extrapolated beyond the study data or hyperbolize study findings. For some insect groups such as some butterflies, bees, and beetles, declines in abundance and diversity have been documented in European studies. Other areas have shown increases in some insect species, although trends in most regions are currently unknown. It is difficult to assess long-term trends in insect abundance or diversity because historical measurements are generally not known for many species. Robust data to assess at-risk areas or species is especially lacking for arctic and tropical regions and a majority of the southern hemisphere.

Conservation

While biodiversity loss is a global problem, conserving habitat for species of insects is uncommon and generally of low priority, although there are exceptions. More commonly insect conservation occurs indirectly, either through the setting aside of large portions of land using "wilderness preservation" as the motive, or through protection of "charismatic vertebrates". Some studies estimate that global insect populations are in rapid decline, perhaps by as much as 80% in recent decades. The windshield phenomenon describes people noticing vastly fewer insects flying into the path of their cars after long drives, and this may reflect worldwide loss of insect abundance.

Single-species insect conservation can preserve other species indirectly; this preservation-by-default is referred to as the umbrella effect. Showy insects such as butterflies or large, colourful beetles serve as flagship species, and can expand public awareness and financial contributions for conservation efforts. Wealthy nations such as the United States do list species of concern, and occasionally insects are placed on its Endangered Species List. In 2017 this list had classified over 80 insects as endangered species, the majority of them beetles or butterflies; a significant percentage of these listed insects are native only to the Hawaiian Islands. Migratory species, such as the well-known monarch butterfly (Danaus plexippus), are in need of special conservation methods. One species may require several habitat locations, even across international boundaries, for the different periods of their migratory patterns.

Insect conservation has been labelled in the past as a concern only for the affluent. The developing country of Papua New Guinea has a "happily ever after" ending in their attempts to preserve the world's largest butterfly, Queen Alexandra's birdwing (Ornithoptera alexandrae). This species is restricted to a very small range of habitat due to specificity in their diet. In the international market of insect collecting, the butterfly can retrieve up to US$2000. In 1978, the government of Papua New Guinea set up the Insect Farming and Trading Agency (IFTA) to regulate the exploitation and conservation of Queen Alexandra's birdwing and other valuable butterflies.

Agriculture

In agricultural ecosystems, biodiversity is instrumentally important not only for the production of food, but for other ecological services as well, including the recycling of nutrients, regulation of microclimate and local hydrological processes, suppression of undesirable organisms and detoxification of noxious chemicals.

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In the United States alone, pollination by bees accounts for over US$9 billion of economic revenue. According to some estimates, over ⅓ of the human diet can be traced directly or indirectly to bee pollination. Losses of key pollinators have been reported in at least one region or country on every continent except Antarctica, which has no pollinators. The Millennium Ecosystem Assessment  concluded that with the global decline in the amount of pollinators, there is not a complete loss of fruit or seeds, but a significant decrease in quantity and viability in fruits, and a lower number of seeds.

Food (human)

Insects are a nutritional source for much of the animal world. Among humans, over 1000 species of insects have been used as food somewhere in the world. Entomophagy is common in central and southern Africa, Asia, Australia, and Latin America. Termites, crickets, grasshoppers, locusts, beetles, ants, bee brood, and moth larvae are examples of insects that are used as food sources. Insects are high in protein, energy, and a number of minerals and vitamins and can form up to 5-10% of the annual animal protein consumption of certain indigenous groups . Many insects are said to have a nutty flavour, along with a high nutritional content.

Human culture

Early human civilisations held insects as an important element within their cultures. Most famously, scarab beetles were central religious artifacts within Egyptian culture. Insect symbolism, such as the dung beetle portrayed as a potter, is seen in the East as well. The Chinese viewed cicadas as a symbol of birth or immortality, the San of the Kalahari believe that the praying mantis represents creation and patience, and the Greeks also created beautiful representations of scarab beetles using colourful stones.

See also

• Insect ecology

References

1. N. E. Stork, J. McBroom, C. Gely, and A. J. Hamilton (16 June 2015). "New approaches narrow global species estimates for beetles, insects, and terrestrial arthropods" (PDF). PNAS. 112 (24): 7519–7523. doi:10.1073/pnas.1502408112. PMC 4475949. Retrieved 21 September 2017.{{cite journal}}: CS1 maint: multiple names: authors list (link)
2. Smithsonian. "Numbers of Insects (Species and Individuals)". BugInfo. Smithsonian Institution. Retrieved 21 September 2017.
3. ^ Stork, Nigel E. (7 January 2018). "How Many Species of Insects and Other Terrestrial Arthropods Are There on Earth?". Annual Review of Entomology. 63 (1): 31–45. doi:10.1146/annurev-ento-020117-043348.
4. Briggs, John C (October 2017). "Emergence of a sixth mass extinction?". Biological Journal of the Linnean Society. 122 (2): 243–248. doi:10.1093/biolinnean/blx063.
5. Owens, Avalon C. S.; Lewis, Sara M. (November 2018). "The impact of artificial light at night on nocturnal insects: A review and synthesis". Ecology and Evolution. 8 (22): 11337–11358. doi:10.1002/ece3.4557. PMC 6262936. PMID 30519447.
6. Tscharntke, Teja; Klein, Alexandra M.; Kruess, Andreas; Steffan-Dewenter, Ingolf; Thies, Carsten (August 2005). "Landscape perspectives on agricultural intensification and biodiversity and ecosystem service management". Ecology Letters. 8 (8): 857–874. doi:10.1111/j.1461-0248.2005.00782.x.
7. Insect-plant interactions in a crop protection perspective. 2017-01-19. p. 313–320. ISBN 978-0-12-803324-1.
8. Braak, Nora; Neve, Rebecca; Jones, Andrew K.; Gibbs, Melanie; Breuker, Casper J. (November 2018). "The effects of insecticides on butterflies – A review". Environmental Pollution. 242 (Pt A): 507–518. doi:10.1016/j.envpol.2018.06.100. PMID 30005263.
9. Wagner, David L.; Van Driesche, Roy G. (January 2010). "Threats Posed to Rare or Endangered Insects by Invasions of Nonnative Species". Annual Review of Entomology. 55 (1): 547–568. doi:10.1146/annurev-ento-112408-085516. PMID 19743915.
10. Sánchez-Bayo, Francisco; Wyckhuys, Kris A.G. (April 2019). "Worldwide decline of the entomofauna: A review of its drivers". Biological Conservation. 232: 8–27. doi:10.1016/j.biocon.2019.01.020.
11. Saunders, Manu (16 February 2019). "Insectageddon is a great story. But what are the facts?". Ecology is not a dirty word. Retrieved 24 February 2019.
12. ^ "Global Insect Biodiversity: Frequently Asked Questions" (PDF). Entomological Society of America. Retrieved 6 March 2019.
13. US Fish and Wildlife Service. "Conserving the Nature of America". ECOS Environmental Conservation Online System. US Fish and Wildlife Service. Retrieved 21 September 2017.
14. W. S. Robinson, R. Nowogrodski & R. A. Morse. (1989). "Pollination parameters". Gleanings in Bee Culture. 117: 148–152.
15. S. E. McGregor (1976). Insect pollination of cultivated crop plants. USDA Agriculture Handbook 496, Washington, D.C.
16. Millennium Ecosystem Assessment, 2005. Ecosystems and Human Well-being: Biodiversity Synthesis. World Resources Institute, Washington, D. C.
17. P. S. Cranston & P. J. Gullan (2005). The Insects: An Outline of Entomology. Blackwell, Oxford. ISBN 1-4051-1113-5.

• Biodiversity
• Insect ecology