INSECTS: CHARACTERISTICS, DIVERSITY, USEFULNESS, LARGEST AND THREATENED ONES

INSECTS

Mantid head

Insects have been around longer than any other forms of terrestrial life. They have existed for over 320 million years, evolving from millipedes which in turn evolved for crustaceans in the sea. Cockroaches and termites and dragonflies are the oldest insects..

Insects are the most widely dispersed and the most numerous of an animals. They can be found in the oceans, on polar ice caps and flying over the Himalayas and living in steaming hot volcanic springs. According to one calculation there are about 1,000,000,000,000,000,000,000 (one million trillion) insects in the earth, more than a billion for every human being. In terms of weight, insects account roughly for 85 percent of all animal life forms, All the world’s insect weigh more that 12 times all the world's people.

Insects, centipedes, millipedes, arachnids (including spiders and scorpions) and crustaceans belong to the phylum of arthropods. Arthropods account for three fourths of all known animals. All have exoskeletons made of chitin; a body divided into segments and protected by cuticle; jointed legs arranged in pairs; an open circulatory system with organs bathed in a liquid called hemolymph that is pumped around the body by the heart; and a nervous system comprised of paired nerve chords.

Insects hatch from eggs as larvae or grub that often resemble short, stubby worms. They then become pupa and finally metamorphose into a full-grown insect. As they grow the shed their old skins exoskeletons and grow new ones. Larvae and pupa spend much of their time eating. Unlike bird eggs, insects eggs contain very little yoke or food. Instead the eggs are laid on or near food sources and the young begin eating as soon as they hatch. The primarily purpose of insects is to reproduce.

Websites and Resources on Insects and Bugs: BugGuide bugguide.net ; Amateur Entomologists' Society amentsoc.org ; MDPI Insects mdpi.com/journal/insects; National Geographic on Bugs National Geographic ; Smithsonian bug info si.edu/Encyclopedia_SI/nmnh/buginfo ; Insect Images.org insectimages.org ; Obervations, the Naturalist inaturalist.org/observations ; Safrinet Manual for Entomology and Arachnology SPC web.archive.org ; Books: Insects (Smithsonian Handbooks)

Websites and Resources on Animals: Animal Diversity Web animaldiversity.org ; BBC Earth bbcearth.com; A-Z-Animals.com a-z-animals.com; Live Science Animals livescience.com; Animal Info animalinfo.org ; Encyclopedia of Life eol.org , a project to create an online reference source for every species; World Wildlife Fund (WWF) worldwildlife.org the world’s largest independent conservation body; National Geographic National Geographic ; ; Endangered Animals (IUCN Red List of Threatened Species) iucnredlist.org ; Biodiversity Heritage Library biodiversitylibrary.org

Diversity and Species of Insects

About half of all eukaryotes (all animals, all plants, all fungi, most algae, and protists) are insects (left side of diagram)

Of the 1.5 million or so known species of animals about 80 percent of them are insects. New insects are discovered and named at a rate of thousands a year. Tens of thousands — perhaps millions more — wait to discovered.

The largest animal phylum is Arthropoda, which includes insects, spiders, crustaceans, and their relatives. They have a segmented body, an external skeleton, and jointed limbs, and are sometimes placed in different phyla. Estimates of the number of arthropod species range from 1,170,000 to 5–10 million. By comparison, there are roughly 73,000 vertebrates, or animals with a backbone from humans to birds and fish — these represent less than 5 percent of the known Animal Kingdom, according to the International Union for Conservation of Nature (IUCN). [Source Julia Janicki, Gloria Dickie, Simon Scarr and Jitesh Chowdhury, Reuters. December 6, 2022]

The arthropods — Invertebrate animals with a segmented body covered by an exoskeleton — can be split into 5 Subphyla, including crustaceans, chelicerates (Spiders, ticks and mites, with 110,000 species) and Hexapods (animals with six legs) The hexopods can be split into four classes, including insects and springtails.

Insects can be split into 29 Orders, including Beetles, Lepidoptera (Butterflies and moths) and Flies. With over 387,000 species, beetles make up almost 40 percent of insects and around 24 percent of all animal species. [Source Julia Janicki, Gloria Dickie, Simon Scarr and Jitesh Chowdhury, Reuters. December 6, 2022]

Insects: 1.05 million: True bugs: 100,000; Caddisflies; Beetles: 387,000; Flies: 150,000; Butterflies, moths: 150,000; Bees, Wasps, Ants: 110,000; Rove beetles; Fireflies: 56,000; Scarab beetles: 27,000; Longhorn beetles: 30,000; Weevils: 51,000; Leaf beetles: 32,500; Ground beetles: 40,000; Ladybugs: 6,000; Other beetles: 97,521

450-Million-Year-Old Arthropod Found Preserved in Fool’s Gold

Arthropods are divided into four major groups: 1) insects; 2) myriapods (including centipedes and millipedes); 3) arachnids (including spiders, mites and scorpions); and 4) crustaceans (including slaters, prawn and crabs).

In a study published October 29, 2024 in the journal Current Biology, scientists said they discovered 450-million-year-old fossil arthropod entirely preserved in pyrite — better known a fool’s gold. The newly named species Lomankus edgecombei has a leg coming out of its head called a “great appendage” that likely helped extinct spider-like creature survive in a very dangerous environment. “As well as having their beautiful and striking golden color, these fossils are spectacularly preserved,” study co-author and University of Oxford paleontologist Luke Parry said in a statement. “They look as if they could just get up and scuttle away.” [Source Laura Baisas, Popular Science, October 30, 2024]

Laura Baisas wrote in Popular Science: Arthropods include modern spiders, horseshoe crabs, centipedes, and insects. This new species of Lomankus is considered a megacheiran — an extinct class of arthropods that are defined by their spined great appendages. This diverse group thrived during the Cambrian Period (538-485 million years ago). They had mostly gone extinct by the Ordovician Period (485-443 million years ago).

The Lomankus fossil was found at the famous Beecher’s Trilobite Bed fossil site in central New York State. This layer of rock contains multiple well-preserved trilobites and other organisms. The animals preserved here lived in a very hostile, dark, and low oxygen environment. However, that environment allowed the fool’s gold to replace some of the body parts after they were buried in the sediment. The results are these golden 3D fossils that can be scanned so scientists can see some hidden details about their anatomy.

“These remarkable fossils show how rapid replacement of delicate anatomical features in pyrite before they decay, which is a signature feature of Beecher’s Trilobite Bed, preserves critical evidence of the evolution of life in the oceans 450 million years ago,” study co-author and Yale University paleontologist Derek Briggs said in a statement.

This new finding gives scientists new clues to a long-standing arthropod puzzle — how they evolved the appendages on their heads. Some species have one or more pairs of legs located at the front of their bodies. These appendages are typically modified for specialized functions, including sensing the environment and capturing prey. Some examples are the antennae of insects and crustaceans and the formidable pincers and fangs of spiders and scorpions. “Today, there are more species of arthropod than any other group of animals on Earth,” said Parry. “Part of the key to this success is their highly adaptable head and its appendages, that has adapted to various challenges like a biological Swiss army knife.”

Other megacheirans used their large first appendage for capturing prey. However, Lomankus appears to have smaller claws, with three long and flexible whip-like flagella at their end. The team believes that Lomankus used this frontal appendage as a way to sense the environment instead of capturing prey. This means that it lived a very different lifestyle to its more ancient relatives from the Cambrian Period. Unlike other megacheirans, Lomankus also appears to lack eyes. It likely would have relied on its frontal appendage to sense for and find food in the dark and low-oxygen environment it lived in. “Rather than representing a ‘dead end’, Lomankus shows us that megacheirans continued to diversify and evolve long after the Cambrian, with the formerly fearsome great appendage now performing a totally different function,” said Parry.

Insect Characteristics

All insects have six legs (three pairs of legs) and a body divided into three distinct parts: 1) a head with a mouth and most of the sensory organs; 2) a muscle-filled thorax that provides platform for the legs; and 3) an abdomen housing the organs used in digestion and reproduction.

All three body are housed on an external skeleton comprised of chiltin and coated with a protein call sclerotin that makes it hard. Chilton is tough, flexible and permeable. It is the same material in crab and lobster shells. It was developed 530 million years ago by crustaceans and has a chemical composition to similar to that of cellulose. The one drawback with an external skeleton is that it has to be shed when the insects grows. Molting refers to process of shedding one exoskeleton and growing another. The energy and time expended in molting is one thing that limits insect size.

Most insects have antennae and large numbers of chemoreceptors on their antennae and legs for the detection of air-borne molecules that the help them find food. Most are deaf. Those that can hear are generally noisemaking insects such as cicadas and crickets. Many also have a long thing mouth part, pointed at the tip and capable if being thrust like a miniature drill deep into a plant or animal and used like a straw to suck juices. Inside the tube are two hollow canals, one for transporting the sucked-up juices into the mouth and the other for secreting saliva.

Insects don't have lungs. Instead they rely on their trachea and a system of tubes running to every part of the body to absorb oxygen and expel carbon dioxide. They are prevented from getting any bigger than they are by their breathing system. The tubes — which are connected to openings called spiracles — work well over short distances but lose their efficiency as they become longer. This is why you don't find crickets the size of crocodiles or ants the size of armadillos. But what about the huge dragonflies that lived before the age of the dinosaurs?

The legs are composed of segments connected by ball and socket joints. The muscles that move the legs are connected to the inner surface of the exoskeleton. This is the opposite of vertebrates in which muscles are attached to the outsides of internal bones.

Largest Insects

The heaviest insect is the larval stage of the Goliath beetle, Goliathus goliatus. The larval stage of the Goliath beetle can weigh up to 115 grams (4.1 ounces) and be 11.5 centimeters (4.5 inches) long. Adult Goliath beetles can weigh up to 100 grams (3.5 ounces). Goliath beetles live tropical forests in Africa. Goliath beetles are part of the scarab beetle family. They are very strong — able to carry up to 850 times their body weight. [Source: Google AI]

The heaviest adult insect is the female giant weta, Deinacrida heteracantha. The female giant weta can weigh up to 71 grams (2.5 ounces). Native to New Zealand and found on on Little Barrier Island, off New Zealand's North Island, they are grasshopper-like bug that can grow to around 7.5 centimeters (3 inches) long according to the Guinness Book of World Records.

Wetas are basically crickets without wings. They have changed little in the last 200 million years. There are ten different species of weta. The largest species lives on Barrier Island off the coast of the North Island. It weighs about 2.5 ounces and is about the size of a mouse. Different species of weta inhabit different regions of the country. The most common species, the tree weta, is found mostly in lowland forests. It is large enough to fill a man's hand and when it is alarmed it kicks with its back legs. [Source: Mark Moffet, National Geographic, November 1991]

Other large insects include stick insects, tarantula hawks, Mydas flies, Queen Alexandra's birdwing, Atlas moths and blue-winged helicopters. The largest lepidopteran (butterfly and moth) species overall is often claimed to be either the Queen Alexandra's birdwing (Ornithoptera alexandrae), a butterfly from Papua New Guinea, or the Atlas moth (Attacus atlas), a moth from Southeast Asia. Both of these species can reach a body length of 8 centimeters (3.1 inches), a wingspan of 28 centimeters (11 inches) and a weight of 12 grams (0.42 ounces). One Atlas moth allegedly had a wingspan of 30 centimeters (12 inches) but this measurement was not verified.

Biggest Known Bug Ever

Christina Larson of Associated Press wrote: As if the largest bug to ever live — a monster nearly 2.6 meters feet long with as many as 64 legs — wasn’t terrifying enough, scientists could only just imagine what the extinct beast’s head looked like. That’s because many of the fossils of these creatures are headless shells that were left behind when they molted, squirming out of their exoskeletons through the head opening as they grew ever bigger — up to 2.6 meters (8 to 9 feet) and more than 100 pounds (50 kilograms). [Source Christina Larson, Associated Press, October 10, 2024]

Now, scientists have produced a mug shot after studying fossils of juveniles that were complete and very well preserved, if not quite cute. The giant bug’s topper was a round bulb with two short bell-shaped antennae, two protruding eyes like a crab, and a rather small mouth adapted for grinding leaves and bark, according to new research published October 2024 in Science Advances.

Called Arthropleura, these were arthropods — the group that includes crabs, spiders and insects — with features of modern-day centipedes and millipedes. But some of them were much, much bigger, and this one was a surprising mix. “We discovered that it had the body of a millipede, but head of a centipede,” said study co-author and paleobiologist Mickael Lheritier at the University Claude Bernard Lyon in Villeurbanne, France. The largest Arthropleura may have been the biggest bugs to ever live, although there is still a debate. They may be a close second to an extinct giant sea scorpion.

How Do Insects Walk on Walls?

Abigail Tucker wrote in Smithsonian magazine: “As soon as microscopes debuted in the 17th century, scientists zoomed in on the feet of common houseflies, marveling at the tiny “soles” that enable insects to scale windowpanes and walk upside down on ceilings. “People were looking for some magic mechanism,” says University of Cambridge zoologist David Labonte. “More than 300 years later, they’re still looking. The minuscule scale and complex geometry of insect feet, not to mention the unruly nature of six-legged research subjects, has meant that when it comes to insect podiatry, says Labonte, “you’d be surprised how much we don’t know.” But he and his colleagues think they’re creeping closer to some answers. [Source: Abigail Tucker, Smithsonian magazine, January-February 2016]

“Scientists have long noticed that insects have wet feet: They leave damp little footprints on flower petals, for instance. (The amount of liquid, an oily hydrocarbon, is minute: around a quadrillionth of a liter per footprint.) It had previously been suspected that the liquid helps glue insects to vertical surfaces through capillary and viscous forces, much as a thin layer of water helps a wet beer glass stick to a tabletop.

“To test this hypothesis, Labonte decided to use — what else? — Indian stick insects. It was not their fitting name but their lackadaisical attitude that attracted him. The bugs, having evolved to resemble twigs, are mostly motionless, and they have the happy habit of extending their front feet, which allowed Labonte to attach wires to their protruding tootsies. With a fiber-optic sensor, he measured how much force it took to lift a foot — at different degrees of wetness — from glass plates at varying speeds. “I’m not sure if they were even awake during all this,” Labonte says of his “stickies.”Labonte learned that the secretion isn’t an adhesive after all, at least not in the predicted manner: Wet and dry feet performed about the same. In fact, Labonte now thinks that the fluid may have the opposite effect, allowing insects to rapidly unstick their feet, by providing a slippery “release layer.” The moisture may even keep insect foot pads supple, and better able to mold to microscopic contours of ceilings and walls, helping them stick in a previously unanticipated way.

“Testing this idea over the next year will involve constructing a millimeter-size rubber model of a bug foot that Labonte can manipulate without worrying about five other flailing feet. Grasping bio-adhesive principles may also inspire advances in manufacturing, like ultra-dexterous robots that can handle and precisely place tiny parts. (Damp sponges, like moist insect feet, could help robots release their grip.) So far the dream of a ready-wear Spiderman suit has less academic traction, but some scientists cling to it nonetheless.

Insect Colors, Markings and Deception

Some beetles get a metallic sheen and dazzling colors not from pigments but from optical features that reflect specific wavelengths of color. These structural colors, which don’t fade and are more brilliant than those produced by pigments, are of great interest to companies that make paint, cosmetics and holograms for credit cards. Investigations of the iridescence in butterflies and beetles and anti-reflective coatings in moth’s eyes have helped produce brighter screens for cell phones and a secret anti-counterfeiting technique.

Bernd Heinrich wrote in Natural History magazine: A specific adaptive sexual attraction within a species can function as a warning signal to other species. Indeed, it is precisely the conspicuous eye-catching displays (of colors as well as scents and sometimes sounds) of many insects that deter predators. With beetles, such as leaf beetles and lady bird beetles, predators learn to associate color patterns and/or scent with noxious secretions and toxins that their potential prey has manufactured or incorporated into their bodies from ingestion of certain food plants. [Source: Bernd Heinrich, Natural History magazine, April 2017]

In his book, “The Liars of Nature and the Nature of Liars”, Lixing Sun, a professor of animal behavior and biology at Central Washington University, addresses fraud and cheating in the animal — and human — world. Elizabeth Kolbert wrote in The New Yorker: One of the slyest, or at least most studied, of nature’s scam artists is the Alcon blue, a lovely, silvery butterfly native to Europe and Central Asia. Female Alcon blues lay their eggs on gentians. The caterpillars that emerge feed on the plants until they have completed three molts. Then, as what is known as fourth instars, they drop to the ground and wait for a passing ant. To identify their kin, ants rely on chemicals called cuticular hydrocarbons. Alcon-blue caterpillars secrete chemicals that are similar enough that ants are tricked into carrying them home. Once inside the nest, the butterfly larvae are nurtured by their formic friends, who feed them as if they were their own. Research by British and Italian scientists shows that the caterpillars employ an additional ruse. They vibrate to produce a sound that ants normally associate with their queen. Alcon-blue butterflies can be such convincing cons that ants will neglect their own larvae to care for them.

Insect anatomy: A- Head B- Thorax C- Abdomen: 1) antenna, 2) ocellus (lower), 3) ocellus (upper), 4) compound eye, 5) brain (cerebral ganglia), 6) prothorax, 7) dorsal blood vessel, 8) tracheal tubes (trunk with spiracle), 9) mesothorax, 10) metathorax, 11) forewing, 12) hindwing, 13) midgut (stomach), 14) dorsal tube (heart), 15) ovary, 16) hindgut (intestine, rectum, anus), 17) anus, 18) oviduct, 19) nerve cord (abdominal ganglia), 20) Malpighian tubules, 21) tarsal pads, 22) claws, 23) tarsus, 24) tibia, 25) femur, 26) trochanter, 27) foregut (crop, gizzard), 28) thoracic ganglion, 29) coxa, 30) salivary gland, 31) subesophageal ganglion, 32) mouthparts

Sex, Sun observes, is fertile ground for deception. Male fireflies from the genus Photinus flash to attract mates. If females are interested, they flash back. Females from the genus Photuris mimic Photinus females’ flashes; then, when males get close enough, they eat them. (Photuris females have become known as the firefly “femmes fatales.”) Some male garter snakes emit faux female pheromones; by confusing their rivals, they increase their chances of scoring. [Source Elizabeth Kolbert, The New Yorker, March 27, 2023]

Blister beetles belonging to the species Meloe franciscanus, in the American West, practice an elaborate, sex-dependent form of kleptoparasitism. Newly hatched Meloe franciscanus larvae hang out together in clumps and collectively emit chemicals that attract male bees. When a male tries to mate with the clump, the larvae attach themselves to his back with special hooks on their feet. If the male is later lucky enough to find an actual mate, the larvae relocate to her back, hitch a ride to her nest, consume the pollen she has gathered, and, for good measure, eat her young.

Frauds like those perpetrated by femme-fatale fireflies and kleptoparasitic beetles obviously take a heavy toll on their victims. This is precisely why, Sun contends, deception is such a powerful evolutionary force. The cheated are under heavy selective pressure to outwit the cheaters, who then come under heavy pressure to refine their techniques. The choice is innovate or die.

Insect Horns

Douglas J. Emlen, a biologist at the University of Montana, has studied insects and other animals with massive horns and other strange weapon-like morphologies. He found that creatures were more likely to develop such weapons when there was some resources that could be monopolized and used to attract females, with the weapons being used to fight off males. The cost of developing and carrying the often heavy and cumbersome weapons is outweighed by the greater access to females, owing to the possession of some prized food source or a place where females could lay their eggs.

Emlen also found, interestingly, that the larger and more fearsome-looking the weapons the less violence there was. The smaller weapons were often quite destructive because the only function they served was as an instrument for fighting. Larger more menacing weapons allowed males to size each other up and determine whether it was worthwhile to engage in battle, with smaller outclassed males avoiding combat if it appeared they were likely to lose. The weapons, when studied over evolutionary time, often started out as small bumps of chiton or bone and then grew bigger.

Emlen wrote in the March 2009 edition of the Annual Review of Ecology, Evolution and Systematics, “The most elaborate weapons rarely inflict real damage to opponents but the structures are very effects at revealing even subtle differences among males in their size, status and physical condition.”

Insect Sex

Thistle Tortoise Beetle (Cassida rubiginosa), an insect with a penis longer than its own body

Natalie Angier wrote in the New York Times: The movie posters for ''Godzilla'' read: ''Size does matter.'' Hey, wipe the scales from your eyes, you overstuffed iguana! Size is not the point: points are the point. Titillators and claspers are the point. So are hooks, knobs and grooves, cerci, epiprocts and paraprocts. How about something that unfolds blade by blade, like a Swiss Army knife — or the phallus of a male oriental cockroach? If big is the best you can do, darling 'Zilla, no wonder you've been a box office snore. [Source: Natalie Angier, New York Times, July 7, 1998]

According to Smithsonian.org “For the male praying mantis, mating can be deadly. That’s because the female of the species is, quite literally, a maneater. Male mantises frantically pursue a mate just before winter sets in, when they are facing an imminent, slow death. Perhaps that’s why they don’t seem to mind the second option: Being decapitated and eaten alive mid-fornication.

“Why do the female bugs turn cannibalistic mid-shag? Sex takes a lot of energy, and devouring their partner is a great source of nutrition that boosts her ability to produce fertilized eggs. She’ll start with the head, because male mantises can actually keep at it for a while without it. (In one documented case, a female ate her mate’s head before they got busy and he still did the deed.) As a male perishes, his abdomen spasms, pumping sperm into the partner and thus increasing the likelihood of mating success. When it’s all said and done, the female gobbles up her mate’s carcass, his lifeless body. A gruesome way to go, but at least he didn’t die cold and alone? [Source: Katherine J. Wu , Rachael Lallensack, Smithsonianmag.com, February 14, 2020]

Male-Female Cave Insects with Reversed Sex Organs

Will Dunham of Reuters wrote: This may be the role reversal to end all role reversals. In April 2014, scientists described four insect species that dwell in extremely dry caves in Brazil, feed on bat guano and possess what the researchers called an “evolutionary novelty.” . The females have an elaborate, penis-like organ while the males have a vagina-like opening into which females insert their organ during mating sessions that last 40 to 70 hours, the scientists reported in the journal Current Biology. The researchers said these attributes make the four species of the insect genus Neotrogla unique in the world. “Evolution of novelties like a female penis is exceptionally rare. That’s why I was really surprised to see the structure,” entomologist Kazunori Yoshizawa of Japan’s Hokkaido University said. [Source: Will Dunham, Reuters, April 18, 2014]

Yoshizawa said that although sex-role reversal has been documented in several different types of animals, these insects are the sole example in which the “intromittent organ” — the male sex organ — is reversed, Yoshizawa said. The Neotrogla insects are small — one tenth to one and a half tenths of an inch long (2.7 mm-3.7 mm) — and superficially look like flies, with nothing particularly unusual about their appearance aside from their genital structures.

The scientists call the female penis-like structure a gynosome. During mating, a female inserts it into a male and receives sperm. Once inserted, part of the gynosome inflates and spines internally anchor the male and female insects together.

Yoshizawa said the females of Neotrogla can hold male mates coercively using their gynosome. “Because the female anchoring force is very strong, a male’s strong resistance may cause damage to his genitalia. Therefore, it is very likely that entire mating processes are controlled actively by females, whereas males are rather passive,” Yoshizawa said.

A Brazilian researcher who was studying cave ecosystems first came across the insects, then enlisted an insect expert to examine the previously unknown bugs. It was at that point that the unique attributes of the female Neotrogla were discovered, leading to the current study. Yoshizawa cited other unusual examples of sex organs among animals, including female seahorses that use an organ to deposit eggs within a male’s brood pouch and a kind of mite whose females have a long genital tube. By the definition of female — an organism that produces egg cells that are larger than the sperm cells produced by males — “even with the penis-like intromittent organ, females of Neotrogla are still female,” Yoshizawa said. But Yoshizawa added: “Females of Neotrogla likely represent the most ‘macho’ females among animals discovered to date.”

Insects from Different Orders (right to left):
Row 1: A) Common scorpionfly (Panorpa communis); B) March brown mayfly (Rhithrogena germanica); C) Head louse (Pediculus humanus capitis)
Row 2: A) Blue emperor (Anax imperator); B) Double drummer (Thopa saccata); C) Silverfish (Lepisma saccharinum)
Row 3: A) Foam grasshopper (Aularches miliaris); B) Dog flea (Ctenocephalides canis);
C) Chrysopa perla
Row 4: A) European earwig (Forficula auricularia); B) Old World swallowtail (Papilio machaon); C) European stag beetle (Lucanus cervus)
Row 5: A) Vinegar fly (Drosophila melanogaster); B) European mantis (Mantis religiosa); C) Northern harvester termite (Hodotermes mossambicus)
Row 6: A) German wasp (Vespula germanica); B) Phyllium philippinicum; C) Dichrostigma flavipes

Do Insects Possess Consciousness?

Evan Bush of NBC News wrote: Bees play by rolling wooden balls — apparently for fun. This discovery serves as indications that the more scientists test animals, the more they find that many species may have inner lives and be sentient (able to perceive or feel things). A surprising range of creatures have shown evidence of conscious thought or experience, including insects, fish and some crustaceans. Prof Jonathan Birch of the London School of Economics said these experiments are part of an expansion of animal consciousness research over the past 10 to 15 years. “We can have this much broader canvas where we’re studying it in a very wide range of animals and not just mammals and birds, but also invertebrates like octopuses, cuttlefish,” he said. “And even increasingly, people are talking about this idea in relation to insects.” [Source: Evan Bush, NBC News, April 20, 2024]

Abigail Tucker wrote in Smithsonian magazine: At a local meeting of the worldwide science and drinking club Nerd Nite in a Sydney, Australia, pub, honeybee scientist Andrew Barron began chatting with philosopher Colin Klein, who initially swatted away the idea of insect consciousness. After all, insect brains are tiny and have just a million or so neurons, compared with a human’s average of 86 billion. Like many of us, Klein had assumed that insects are just collections of reflexes — that they are “dark inside,” he says — and this assumption jibed nicely with his habit of flushing the enormous cockroaches at his apartment down the toilet. [Source: Abigail Tucker, Smithsonian magazine, July-August 2016]

“But then the two Macquarie University professors began to explore the research. One prominent theory holds that the core of human consciousness is not our impressive neocortex, but our much more primitive midbrain. This simple structure synthesizes sensory data into a unified, egocentric point of view that lets us navigate our world.

“Insects, Barron and Klein now argue, have midbrain-like structures, including a “central complex,” that seem to allow bugs to similarly model themselves as they move through space. They cite evidence ranging from a study that used microelectrodes to look at fly brain activity, to seemingly macabre research showing that when a jewel wasp injects venom into a cockroach’s central complex, the zombiefied prey will allow itself to be led by the antennae into its predator’s lair.

“While the human midbrain and the insect brain may even be evolutionarily related, an insect’s inner life is obviously more basic than our own. Accordingly, bugs feel something like hunger and pain, and “perhaps very simple analogs of anger,” but no grief or jealousy. “They plan, but don’t imagine,” Klein says. Even so, insects’ highly distilled sense of self is a potential gift to the far-out study of consciousness. Probing the insect brain could help quantify questions of what it means to think that vexed the likes of Aristotle and Descartes, and could even aid the development of sentient robots.“On the other hand, it complicates daily life. “I still flush,” Klein says of his cockroaches. “But I hesitate.”

Importance of Insects

“Insects are the food that make all the birds and make all the fish,” David Wagner, who works at the University of Connecticut, told Reuters. “They’re the fabric tethering together every freshwater and terrestrial ecosystem across the planet.” [Source Julia Janicki, Gloria Dickie, Simon Scarr and Jitesh Chowdhury, Reuters. December 6, 2022]

According to Reuters ; Their importance to the environment can’t be understated, scientists say. Insects are crucial to the food web, feeding birds, reptiles and mammals such as bats. For some animals, bugs are simply a treat. Plant-eating orangutans delight in slurping up termites from a teeming hill. Humans, too, see some 2,000 species of insects as food.

But insects are so much more than food. Farmers depend on these critters pollinating crops and churning soil to keep it healthy, among other activities. Insects pollinate more than 75 percent of global crops, a service valued at up to $577 billion per year, the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES) says.

In the United States, insects perform services valued in 2006 at an estimated $57 billion per year, according to a study in the journal BioScience. Dung beetles alone are worth some $380 million per year to the U.S. cattle industry for their work breaking down manure and churning rangeland soil, the study found.

With fewer insects, “we’d have less food,” said ecologist Dave Goulson at the University of Sussex. “We’d see yields dropping of all of these crops.” And in nature, about 80 percent of wild plants rely on insects for pollination. “If insects continue to decline,” Goulson said, “expect some pretty dire consequences for ecosystems generally — and for people.”

Threatened Insects

Research suggests insect populations are declining at an unprecedented rate. As human activities rapidly transform the planet, the global insect population is declining at an unprecedented rate of up to 2 percent per year. According to a Reuters report: As a boy in the 1960s, Wagner would run around his family’s Missouri farm with a glass jar clutched in his hand, scooping flickering fireflies out of the sky. “We could fill it up and put it by our bedside at night,” says Wagner, now an entomologist. That’s all gone, the family farm now paved over with new homes and manicured lawns. And Wagner’s beloved fireflies — like so many insects worldwide — have largely vanished in what scientists are calling the global Insect Apocalypse. [Source Julia Janicki, Gloria Dickie, Simon Scarr and Jitesh Chowdhury, Reuters. December 6, 2022

It’s easy to think insects are doing OK. After all, they’re nearly everywhere — crawling through rainforest canopy, burrowing into soil, skimming freshwater ponds or, of course, flitting through the air. But this is misleading. The world has lost 5 percent to 10 percent of all insect species in the last 150 years — or between 250,000 and 500,000 species, according to a February 2020 study in the journal Biological Conservation. Those losses are continuing, though estimates vary due to patchy data as well as uncertainty over how many insects exist.]

In the tropics, insects can be “extremely hard to identify, because there are vastly more species than (we) are used to,” evolutionary ecologist Daniel Janzen of the University of Pennsylvania professor, told Reuters. “There are more species within 100 kilometres of my dwelling in a national park in northwestern Costa Rica than in all of Europe.”

Not knowing exactly what’s out there makes it harder to detect trouble. One April 2020 analysis in the journal Science suggested the planet is losing about 9 percent of its land-dwelling insect population each decade. Another January 2021 paper tried to paint a clearer picture by synthesizing more than 80 insect studies and found that insect abundance is declining around 1 percent to2 percent per year. For comparison, the human population is growing at slightly less than 1 percent per year.

“Even at the low end of 1 percent a year, after just 40 years you’re down more than one-third of species and one-third of individuals — a third of the entire tree of life lost,” said Wagner, who led the 2021 metastudy, published in the Proceedings of the National Academy of Sciences. But the reality is likely worse. Wagner’s team offered an “incredibly conservative” loss estimate, he said, noting that many insect studies are conducted in protected areas such as nature reserves. Degraded farmland or cities would likely reveal far fewer insects.

The decline of insects also affects many other non-insect animals. In North America, nearly all songbirds feed insects to their young. But since 1970, the number of birds in the United States and Canada has fallen by 29 percent, or roughly 2.9 billion, which scientists theorize is tied to having fewer insects in the world. Some research also has linked insecticide use with declines in barn swallows, house martins, and swifts. “Nature is just eroding away very slowly,” Wagner said. As insects disappear, “we’re losing the limbs and the twigs of the tree of life. We’re tearing it apart. And we’re leaving behind a very simplified and ugly tree.”

Why Insect Numbers Are Decreasing

Deforestation, pesticide use, artificial light pollution and climate change have all been named as reasons of the decline of insects. According to Reuters: The demise of insects can’t be attributed to any single cause. Populations are facing simultaneous threats, from habitat loss and industrial farming to climate change. Nitrogen overloading from sewage and fertilizers has turned wetlands into dead zones; artificial light is flooding out nighttime skies; and the growth of urban areas has led to concrete sprawl. [Source Julia Janicki, Gloria Dickie, Simon Scarr and Jitesh Chowdhury, Reuters. December 6, 2022]

“Until recently, loss of land was the single greatest driver” of the decline, Wagner said. “But climate change is becoming a far more severe and ominous threat by drying out parts of the planet that were chronically wet. And that is absolutely catastrophic for a lot of insects.”

The introduction of non-native plants, which can dominate new environments, has also hurt insects. Because many insects have evolved to feed on or fertilize a single plant species, the disruption of the plant world can have an outsized effect. For example, the Tegeticula moth species pollinates California’s famed Joshua trees, with the succulent providing the only food source for the moth’s offspring. If Joshua trees were to disappear, so too could the moth. And vice versa.

While the situation is bleak for insects at large, a few species are thriving. “It’s generally the pest insects that are thriving because they’re the ones that breed faster and are favored by human conditions, like all the waste we produce for them to lay their eggs in,” said Sussex’s Goulson.

Climate change is also giving some nuisance species a boost. Rising temperatures are driving major outbreaks of mountain pine bark beetles, which in two decades have decimated roughly 100,000 square miles (260,000 square kilometers) of North American forest. And with warmer, wetter weather, two disease-spreading mosquitoes Aedes aegypti and Aedes albopictus are expected to expand in Asia, North America and Europe, putting an additional 2.3 billion people at risk from dengue fever by 2080, a June 2019 Nature Microbiology study estimated.

IUCN data from 2021 show that, of the roughly 1 million known insect species, the conservation status of only about 1 percent has been assessed. So while scientists are certain that insect abundance is dropping fast, they aren’t entirely sure which insects are most at risk. Because the insect class is so vast, that 1 percent of insects assessed represents roughly the same number of species as the 100 percent of birds assessed, and twice the number of mammals assessed. Backboned animals, particularly charismatic mammals, tend to attract more research funding than insects. A European research project looking at a vertebrate species, for example, receives nearly 500 times more funding on average than an invertebrate study.Out of all insects assessed, one in five — or 2,270 in total — is considered threatened.

Image Sources: Wikimedia Commons

Text Sources: Mostly National Geographic articles. David Attenborough books, Live Science, New York Times, Washington Post, Los Angeles Times, Smithsonian magazine, Natural History magazine, Discover magazine, Times of London, The New Yorker, Time, Newsweek, Reuters, AP, AFP, Lonely Planet Guides, Compton’s Encyclopedia and various books and other publications.

Last updated February 2025