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. [1] [2]
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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. [1] [2]
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. [3] Between 950,000–1,000,000 of all described animal species are considered insects, so over 50% of all described eukaryotes (1.8 million species) are insects (see illustration). With only 950,000 known non-insects, if the actual total 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 identified orders of insects, five dominate in terms of numbers of described species, namely Coleoptera (beetles), Lepidoptera (butterflies and moths), Diptera (flies and mosquitoes), Hymenoptera (ants, bees, wasps and sawflies) and Hemiptera (true bugs, e.g. cicadas, aphids, leafhoppers, bed bugs and assassin bugs). At least 900,000 described species — about 90% of all known insects — belong to the five aforementioned orders, each of which has over 100,000 species, while the next (sixth) most diverse order, Orthoptera (locusts, grasshoppers and crickets), has just under 24,000 species.
| Order | Extant species described |
|---|---|
| Archaeognatha | 513 |
| Zygentoma | 560 |
| Ephemeroptera | 3,240 |
| Odonata | 5,899 |
| Orthoptera | 23,855 |
| Phasmatodea | 3,014 |
| Embioptera | 463 |
| Grylloblattodea | 34 |
| Mantophasmatodea | 15 |
| Plecoptera | 3,743 |
| Dermaptera | 1,978 |
| Zoraptera | 37 |
| Mantodea | 2,400 |
| Blattodea | 7,314 |
| Psocoptera | 5,720 |
| Phthiraptera | 5,102 |
| Thysanoptera | 5,864 |
| Hemiptera | 103,590 |
| Hymenoptera | 116,861 |
| Strepsiptera | 609 |
| Coleoptera | 386,500 |
| Neuroptera | 5,868 |
| Megaloptera | 354 |
| Raphidioptera | 254 |
| Trichoptera | 14,391 |
| Lepidoptera | 157,338 |
| Diptera | 155,477 |
| Siphonaptera | 2,075 |
| Mecoptera | 757 |
The fossil record concerning insects stretches back for hundreds of millions of years. It suggests there are ongoing background levels of both new species appearing and extinctions. Very occasionally, the record also appears to show mass extinctions of insects. The Permian–Triassic extinction event saw the greatest level of insect extinction, with the Cretaceous–Paleogene being the second highest. Insect diversity has recovered after past mass extinctions, due to periods where new species originate with increased frequency, though the recovery can take millions of years. [4]
Several studies seemed to indicate that some insect populations are in decline in the late 20th and early 21st centuries, and has also been popularized as the windshield phenomenon. For many studies, factors such as abundance, biomass, and species richness are often found to be declining for some, but not all locations in many studies; some species are in decline while others are not. [5] Every species is affected in different ways by changes in the environment, and it cannot be inferred that there is a consistent decrease across different insect groups. When conditions change, some species easily adapt to the change while others struggle to survive. [6]
Concerns of declines in insect abundance in the holocene have been attributed to habitat loss from land use changes such as urbanization or agricultural use, [7] [8] pesticide use, [9] invasive species, [10] and artificial lighting. [11] The use of increased quantities of insecticides and herbicides on crops have affected not only non-target insect species, but also the plants on which they feed. Climate change and the introduction of exotic species that compete with the indigenous ones put the native species under stress, and as a result they are more likely to succumb to pathogens and parasites. [6]
As of 2017, at least 66 insect species extinctions had been recorded in the previous 500 years, which generally occurred on oceanic islands. [12] For 203 insect species that had IUCN-documented population trends in 2013, 33% were in decline with variation in documented species across orders. [13] Most scientific and public attention has been focused on the conservation of larger, charismatic vertebrates, and relatively fewer studies have been done on insect groups, especially Diptera, Orthoptera and Hemiptera. Data from the past from which to calculate trends is largely unavailable, and what does exist is mostly related to Western Europe and North America. Insect population assessments that have been undertaken were largely concentrated on the more popular insect groups, butterflies and moths, bees, dragonflies and beetles. [14]
Some studies have suggested a large proportion of insect species (up to a third of the known species) are threatened with extinction in the 21st century, such as a 2019 review by Sánchez-Bayo and Wyckhuys, [14] though ecologist Manu Sanders notes that many of these findings are often biased limited to specific geographic areas and specific groups of species. [15] The methodology of the Sánchez-Bayo & Wyckhuys study has been questioned; the search string used to sift through the scientific literature was "(insect* + decline* + survey)". This meant that the authors identified studies finding insect declines, but may have missed those that found increases in insect populations or stability. [5] [15] In assessing the study methodology, an editorial in Global Change Biology stated, "An unbiased review of the literature would still find declines, but estimates based on this 'unidirectional' methodology are not credible. [5] However, according to the authors of that review "more than half of the surveys were obtained from references cited in other reports" and "the 73 insect surveys cover all species in a particular taxon – irrespective of them exhibiting declines, stable or increasing trends in their distribution or abundance". [16] Entomology professor Simon Leather suggested that media reports of an "Ecological Armageddon" may be exaggerated and advocated for more funding to allow better collection of long term data on the decline. [17]
Claims of pending mass insect extinctions or "insect apocalypse" based on a subset of studies have been popularized in news reports, but often make claims extrapolated beyond the study data or hyperbolize study findings. [18] The Entomological Society of America has stated there are not sufficient data to predict an imminent mass extinction of insects. [18] 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. [18]
 | This section needs additional citations for verification .(May 2024) |
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. [19] 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.
In agricultural ecosystems, biodiversity is important for the production of food and for ecological services such as the recycling of nutrients, regulation of microclimate and local hydrological processes, and biological control of pests.[ citation needed ]
In the United States alone, pollination by bees accounts for over US$9 billion of economic revenue. [20] According to some estimates, over ⅓ of the human diet can be traced directly or indirectly to bee pollination. [21] 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 [22] 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.
The Holocene extinction, or Anthropocene extinction, is the ongoing extinction event caused by humans during the Holocene epoch. These extinctions span numerous families of plants and animals, including mammals, birds, reptiles, amphibians, fish, and invertebrates, and affecting not just terrestrial species but also large sectors of marine life. With widespread degradation of biodiversity hotspots, such as coral reefs and rainforests, as well as other areas, the vast majority of these extinctions are thought to be undocumented, as the species are undiscovered at the time of their extinction, which goes unrecorded. The current rate of extinction of species is estimated at 100 to 1,000 times higher than natural background extinction rates and is increasing. During the past 100–200 years, biodiversity loss and species extinction have accelerated, to the point that most conservation biologists now believe that human activity has either produced a period of mass extinction, or is on the cusp of doing so. As such, after the "Big Five" mass extinctions, the Holocene extinction event has also been referred to as the sixth mass extinction or sixth extinction; given the recent recognition of the Capitanian mass extinction, the term seventh mass extinction has also been proposed for the Holocene extinction event.
Biodiversity is the variability of life on Earth. It can be measured on various levels. There is for example genetic variability, species diversity, ecosystem diversity and phylogenetic diversity. Diversity is not distributed evenly on Earth. It is greater in the tropics as a result of the warm climate and high primary productivity in the region near the equator. Tropical forest ecosystems cover less than one-fifth of Earth's terrestrial area and contain about 50% of the world's species. There are latitudinal gradients in species diversity for both marine and terrestrial taxa.
Moths are a group of insects that includes all members of the order Lepidoptera that are not butterflies. They were previously classified as suborder Heterocera, but the group is paraphyletic with respect to butterflies and neither subordinate taxon is used in modern classifications. Moths make up the vast majority of the order. There are approximately 160,000 species of moth, many of which have yet to be described. Most species of moth are nocturnal, although there are also crepuscular and diurnal species.
A pollinator is an animal that moves pollen from the male anther of a flower to the female stigma of a flower. This helps to bring about fertilization of the ovules in the flower by the male gametes from the pollen grains.
Conservation biology is the study of the conservation of nature and of Earth's biodiversity with the aim of protecting species, their habitats, and ecosystems from excessive rates of extinction and the erosion of biotic interactions. It is an interdisciplinary subject drawing on natural and social sciences, and the practice of natural resource management.
Pollination is the transfer of pollen from an anther of a plant to the stigma of a plant, later enabling fertilisation and the production of seeds. Pollinating agents can be animals such as insects, for example beetles or butterflies; birds, and bats; water; wind; and even plants themselves. Pollinating animals travel from plant to plant carrying pollen on their bodies in a vital interaction that allows the transfer of genetic material critical to the reproductive system of most flowering plants. When self-pollination occurs within a closed flower. Pollination often occurs within a species. When pollination occurs between species, it can produce hybrid offspring in nature and in plant breeding work.
Pollinator decline is the reduction in abundance of insect and other animal pollinators in many ecosystems worldwide that began being recorded at the end of the 20th century. Multiple lines of evidence exist for the reduction of wild pollinator populations at the regional level, especially within Europe and North America. Similar findings from studies in South America, China and Japan make it reasonable to suggest that declines are occurring around the globe. The majority of studies focus on bees, particularly honeybee and bumblebee species, with a smaller number involving hoverflies and lepidopterans.
Ecosystem diversity deals with the variations in ecosystems within a geographical location and its overall impact on human existence and the environment.
Coextinction and cothreatened refer to the phenomenon of the loss or decline of a host species resulting in the loss or endangerment of another species that depends on it, potentially leading to cascading effects across trophic levels. The term was originated by the authors Stork and Lyal (1993) and was originally used to explain the extinction of parasitic insects following the loss of their specific hosts. The term is now used to describe the loss of any interacting species, including competition with their counterpart, and specialist herbivores with their food source. Coextinction is especially common when a keystone species goes extinct.
Entomophily or insect pollination is a form of pollination whereby pollen of plants, especially but not only of flowering plants, is distributed by insects. Flowers pollinated by insects typically advertise themselves with bright colours, sometimes with conspicuous patterns leading to rewards of pollen and nectar; they may also have an attractive scent which in some cases mimics insect pheromones. Insect pollinators such as bees have adaptations for their role, such as lapping or sucking mouthparts to take in nectar, and in some species also pollen baskets on their hind legs. This required the coevolution of insects and flowering plants in the development of pollination behaviour by the insects and pollination mechanisms by the flowers, benefiting both groups. Both the size and the density of a population are known to affect pollination and subsequent reproductive performance.
Economic entomology is a field of entomology, which involves the study of insects that benefit or harm humans, domestic animals, and crops. Insects that pose disadvantages are considered pests. Some species can cause indirect damage by spreading diseases, and these are termed as disease vectors. Those that are beneficial include those that are reared for food such as honey, substances such as lac or pigments, and for their role in pollinating crops and controlling pests.
In zoology, a palynivore /pəˈlɪnəvɔːɹ/, meaning "pollen eater" is an herbivorous animal which selectively eats the nutrient-rich pollen produced by angiosperms and gymnosperms. Most true palynivores are insects or mites. The category in its strictest application includes most bees, and a few kinds of wasps, as pollen is often the only solid food consumed by all life stages in these insects. However, the category can be extended to include more diverse species. For example, palynivorous mites and thrips typically feed on the liquid content of the pollen grains without actually consuming the exine, or the solid portion of the grain. Additionally, the list is expanded greatly if one takes into consideration species where either the larval or adult stage feeds on pollen, but not both. There are other wasps which are in this category, as well as many beetles, flies, butterflies, and moths. One such example of a bee species that only consumes pollen in its larval stage is the Apis mellifera carnica. There is a vast array of insects that will feed opportunistically on pollen, as will various birds, orb-weaving spiders and other nectarivores.
There are several plausible pathways that could lead to an increased extinction risk from climate change. Every plant and animal species has evolved to exist within a certain ecological niche. But climate change leads to changes of temperature and average weather patterns. These changes can push climatic conditions outside of the species' niche, and ultimately render it extinct. Normally, species faced with changing conditions can either adapt in place through microevolution or move to another habitat with suitable conditions. However, the speed of recent climate change is very fast. Due to this rapid change, for example Ectotherm cold-blooded animals may struggle to find a suitable habitat within 50 km of their current location at the end of this century.
Neonicotinoids are a class of neuro-active insecticides chemically similar to nicotine, developed by scientists at Shell and Bayer in the 1980s.
Defaunation is the global, local, or functional extinction of animal populations or species from ecological communities. The growth of the human population, combined with advances in harvesting technologies, has led to more intense and efficient exploitation of the environment. This has resulted in the depletion of large vertebrates from ecological communities, creating what has been termed "empty forest". Defaunation differs from extinction; it includes both the disappearance of species and declines in abundance. Defaunation effects were first implied at the Symposium of Plant-Animal Interactions at the University of Campinas, Brazil in 1988 in the context of Neotropical forests. Since then, the term has gained broader usage in conservation biology as a global phenomenon.
Insects are hexapod invertebrates of the class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body, three pairs of jointed legs, compound eyes, and a pair of antennae. Insects are the most diverse group of animals, with more than a million described species; they represent more than half of all animal species.
Conservation is the maintenance of biological diversity. Conservation can focus on preserving diversity at genetic, species, community or whole ecosystem levels. This article will examine conservation at the species level, because mutualisms involve interactions between species. The ultimate goal of conservation at this level is to prevent the extinction of species. However, species conservation has the broader aim of maintaining the abundance and distribution of all species, not only those threatened with extinction. Determining the value of conserving particular species can be done through the use of evolutionary significant units, which essentially attempt to prioritise the conservation of the species which are rarest, fastest declining, and most distinct genotypically and phenotypically.
An insect hotel, also known as a bug hotel or insect house, is a manmade structure created to provide shelter for insects. They can come in a variety of shapes and sizes depending on the specific purpose or specific insect it is catered to. Most consist of several different sections that provide insects with nesting facilities – particularly during winter, offering shelter or refuge for many types of insects. Their purposes include hosting pollinators.
Biodiversity loss happens when plant or animal species disappear completely from Earth (extinction) or when there is a decrease or disappearance of species in a specific area. Biodiversity loss means that there is a reduction in biological diversity in a given area. The decrease can be temporary or permanent. It is temporary if the damage that led to the loss is reversible in time, for example through ecological restoration. If this is not possible, then the decrease is permanent. The cause of most of the biodiversity loss is, generally speaking, human activities that push the planetary boundaries too far. These activities include habitat destruction and land use intensification. Further problem areas are air and water pollution, over-exploitation, invasive species and climate change.
Insects are the most numerous and widespread class in the animal kingdom, accounting for up to 90% of all animal species. In the 2010s, reports emerged about the widespread decline in insect populations across multiple insect orders. The reported severity shocked many observers, even though there had been earlier findings of pollinator decline. There has also been anecdotal reports of greater insect abundance earlier in the 20th century. Many car drivers know this anecdotal evidence through the windscreen phenomenon, for example. Causes for the decline in insect population are similar to those driving other biodiversity loss. They include habitat destruction, such as intensive agriculture, the use of pesticides, introduced species, and – to a lesser degree and only for some regions – the effects of climate change. An additional cause that may be specific to insects is light pollution.
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