FLYING INSECTS: FLIES, DRAGONFLIES, FIREFLIES

FLYING INSECTS

Most flying insects move their wings in long, sweeping strokes (140 to 165 degrees) at roughly 200 beats a second. Bees, wasps and hornets (Order Hymenoptera) have two sets of wings. Flies (Order Diptera) have only one set.

Carnivorous flying insects employ several hunting strategies, including: 1) “hawking,” hunting while in flight using their speed and maneuverability to chase down prey; 2) “sallying,” in which the hunter waits patiently on a perch and then darts out suddenly to grab prey; 3) “gleaning,” hoovering or flying around a spot and picking prey off the ground or vegetation.

With wings beating at 150 times per second in a U-shaped beat, a common blowfly can hoover in the air and fly with exceptional dexterity. It can go from straight-line flight and turn 90 degrees in under 50 milliseconds — a maneuver that would rip apart even the most advanced fighter planes. Ron Fearing, a professor of electrical engineering at Berkeley, who has studied the flight of the insect told National Geographic, “The flying wing is driven by 20 muscles, some of which only fires every forth wing beat, and all you can do is wonder, what on earth just happened there. Some things are just too mysterious and complicated to be able to replicate.”

Fearing has created robot about the size of an insect that is flies like a fly, Modeled after a blowfly, it is powered by tiny electric actuators along its sides. The wings beat up to 275 times per second, even faster than real blowflies. To make such a fly he used micromachines and a rapid prototyping system that allowed him to design the minuscule parts on a commuter, automatically cut and cure them over night and assemble them by hand under a microscope. The fly wing were made of two-micron polyester sheets reinforced with carbon fiber. The robot flies well enough. Fearing is currently attempting to get it to hoover, bank and dive.

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

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

Flying Insects Aren’t Attracted to Light at Night, They’re Confused By It

At night, it’s not unusual to see a bunch of moths and other insects flying around a porch light or street lamp. It has long been assumed they were attracted to the light like “moths to a flame.” But that is not the case. Instead they are trapped in a disorienting orbit around the artificial light, according to study published January 30, 2024 in the journal Nature Communications. [Source: Taylor Nicioli, CNN, February 8, 2024]

Taylor Nicioli of CNN wrote: By using motion-capture cameras — and filming with infrared illumination so as not to disrupt the creatures’ vision — the researchers showed that when the insects flew around a light source, they were tilting their backs toward the light and keeping their bodies in that direction. By maintaining this orientation, the hapless critters created odd orbits and steering patterns, according to the study.

When artificial light does not interfere, nocturnal insects keep their backs pointed toward whatever direction is brightest, which is typically the sky versus the ground. This evolutionary trick has helped the critters know which way is up and keep them level during their night flights. However, when the insects pass by an artificial light source, they become disoriented, believing that the human-made lighting is the sky, said co-lead study author Samuel Fabian, an entomologist and postdoctoral researcher at Imperial College London’s department of bioengineering.

“Insects in the air don’t inherently know which way is up, they don’t have a very good way of measuring that. … It’s assuming the light is the direction of up, but it’s wrong. And if you tilt, that’s going to create sort of weird steering patterns, in the same way that if you were riding a bike and you tilt over to one side, you’re going to get to steer in a big circle, it’s all going to go a bit funky,” Fabian said.

The study team compiled hundreds of slow-motion videos capturing the behaviors of butterflies, moths, bees, wasps, dragonflies and damselflies, and found that the critters were not attracted to faraway lights. The insects only appeared to be drawn in when passing a light that was nearby. Consistently, the overwhelming majority of study subjects tilted their backs toward the light, even if doing so prevented sustained flight.

“Maybe when people notice it, like around their porchlights or a streetlamp, it looks like they are flying straight at it, but that’s not the case,” said co-lead study author Yash Sondhi, a postdoctoral researcher at the Florida Museum of Natural History, in a news release. Sondhi contributed to the research while a doctoral student of biology at Florida International University in Miami.

The team observed three common responses to the light source made by the insects, including orbiting the light, stalling — which caused the insect to steeply climb above the light — and inverting, in which the insect flipped over and crashed into the ground. Some fast-flying insects, such as dragonflies, remained in orbit for minutes at a time, going swiftly round and round the light fixture, Fabian said. In one experiment, the researchers emulated the night sky by shining a light on a white sheet oriented above and found the insects were able to navigate under it without issues. If the insects were inherently seeking the light, they would have crashed into the sheet, Fabian said. “The behaviors of flying insects in the presence of artificial light close to the ground are non-uniform and surprisingly complex in a way that had not really been documented well previously,” said Floyd Shockley, the collections manager for the department of entomology at the Smithsonian National Museum of Natural History in Washington, DC.

Past theories on why many insects erratically fly around light sources have included the idea that they are drawn to heat and that the creatures — particularly those that ancestrally lived in caves and holes in trees — believe the light source is an escape to the outside. The most common one has been that insects are confusing the light with the moon, which they use as a compass cue. Since the critters are not flying directly toward the light, and the behavior has also been observed in species that are not migratory and do not use compass cues, these old theories no longer seem likely, Fabian said.

Houseflies and Hoverflies

Hoverflies

The housefly is regarded by some as the most aerodynamically sophisticated creature on the planet: superior to any bird. It can make six turns a second, fly straight up and down and backwards, land on a ceiling and a do a somersault in mid air — and do all this with a brain that is smaller than sesame seed.

Houseflies evolved millions of years ago and were among the first animals to take to the air. They only have a dozen or so muscles used for maneuvering. Their acrobatic skill is attributed to a wide range of senors, including its compound eyes which are excellent at detecting motions and sensitive hairs and antennae that can sense even slight wind motions and directions. Roughly two thirds of a housefly’s nervous system is devoted to processing sensory and visual information. It can digest huge amounts of data and make a decision based on it in milliseconds.

Many scientists claim that hoverflies are the best fliers. They can hover in the air, dart of to one place and direction and fly right back to the original spot. Studies with some flies show that they can execute sophisticated areal moves with equilibrium organs in their backs that serve as gyroscopes.

Laura Geggel wrote in Live Science: That hairy appendage dangling out of a fly's mouth may look like a tongue, but it's not. Scientists call it the labellum, and it's the primary taste organ for the Drosophila fruit fly, according to a report from Indiana Public Media. The labellum is attached to the fly's straw-like proboscis, which allows the pest to slurp up food. A word to the wise: Put your leftovers away if you've got a fly problem. These buzzing beasties puke saliva and digestive juices onto food before eating it, because these acids dissolve the food the fly wants to suck up, according to HowStuffWorks. [Source Laura Geggel, Live Science, July 11, 2024]

Maggots as a Cure

Doctors are increasingly taking a serious look at maggots (flesh-eating fly larvae) as a treatment for severely wound and ulcerated legs because the treatment has proven to be effective, easy and cheap. Maggots are very good at cleaning festering, gangrenous wounds. They are used on diabetics and other people who have a hard time getting wounds to heal by pressing them into dying flesh with wire-mesh bandages. Greenfly larvae are given patients who are assured that the maggots will not burrow into their skin. Maggots are especially effective fighting the super bug antibiotic-resistant staphylococcus aureus.

Maggots eat dead tissues and killing bacteria that could block the healing process. The use of maggots was common in the 19th century and early 20th century but fell out of favor after antibiotic were invented. The practice was revived out of concerns of patient using too many antibiotics.

Among the cultures that have that have used maggots have been Aboriginals in Australia, hill tribes in Burma and the ancient Mayans. Napoleon’s doctor commented on their effects. In World War I doctors discovered that soldiers that had been left untreated had healthy, pink flesh under their maggot-infested wounds. Their efforts to promotes maggots as a form of treatment was dismissed after antibiotics became widely embraced.

Dr. Thomas Stuttaford wrote in the Times of London, “The value of maggots in removing irretrievably wound-damaged tissue came into its own in World War I...In trench warfare, wounded soldiers often had to lie in no man’s land for hours, sometimes a day or two, until they could be brought back by patrols after dark...My father , who was a doctor for three years in the trenches, said he always reassured the casualties whose wounds were playing host to maggots that, disgusting as they looked, they would hasten the healing of the their wounds....Claims that maggots may have antiseptic action that destroys bacteria are quite possibly true but more important is that they remove the decaying flesh that makes a wonderful culture on which bacteria flourish.”

Researchers have found that maggot treatment for a severe, festering wounds can reduce the duration time of the treatment from weeks to days and cut the cost from $4,400 to $600. A study by maggot-supplier Zoobiotoc published in the Journal of Wound Care found that an ulcerated leg could be treated effectively with12 boxes of maggots, each containing 300 maggots. To treat the same wound with hydrogel, the common treatment for leg ulcers, cost $4,400.

Dragonflies

Dragonflies are the first known flying creatures to appear on earth. They emerged about 320 million years ago. Most were around the size of modern dragonflies but with an absence of predators some with a wingspan of 70 centimeters evolved. They were largest insects that ever existed. Except for their size modern dragonflies have changed little since then.

Dragonflies have two sets of wings and simple joints between them. They can only move their wings up and down and can not fold them back. Even so they are excellent fliers, maneuvering all over the place and reaching speed of 30kph. They get around during the day using mosaic eyes and sensory hairs in the front of their body. Their inability to see at night keeps them grounded after the sun goes down.

Dragonflies and damselflies belong to the Odonata order of insects which embraces more than 6,000 species. Damselflies are generally smaller than dragonflies. Their wings fold back over their backs when they are at rest while dragonflies keep their wings extended outward. All Dragonflies and damselflies are predators who rely on their excellent sense of sight provided by their large compound eyes when seeking out prey. Dragonflies on the hunt use their front legs like tiny baskets to collect prey, mostly smaller insects. Large dragonflies will feed on smaller dragonflies.

Dragonflies are totally carnivorous. They don’t munch on plants nor sip nectar. Their entire diet consists of live prey they catch themselves. Many species hunt while in flight using their speed and maneuverability to chase down prey. This hunting method is known to scientists as “hawking.” Another common technique, known as “sallying,” is for the dragonflies to wait patiently on a perch and then dart out suddenly to grab prey. A third technique, “gleaning,” involves hoovering or flying around a spot and picking prey off the ground or vegetation.

Dragonfly Development

Dragonflies begin as eggs deposited in water. They live in the water as predatory larvae called naiads after Greek water spirits. They have extendable jaws that snap shut with lightning speed to snare prey which then have their juices sucked out of them by the naiad’s sharp-tipped strawlike mouthpiece. The first stage larvae are so small they can feed only on water fleas but as they get bigger they can prey on small fish, tadpoles and even frogs.

Dragonflies often emerge from their larval skin at night. Their wings harden usually by morning but usually don’t fly until later because their bodies take several days to fully harden and develop their characteristic bright colors. After they emerge from the larval stage they often live for only a couple of months. While they are molting the are vulnerable to attacks from birds.

Dragonfly Sex

Dragonflies have an unusual way of reproducing. Males produce sperm in one organ and then transfer it another organ that is called a penis but is not really one. In mid air the male clasps the female who curves her body until it reaches the penis. The mating take about an hour. During the first 20 minutes the penis locks itself inside the female with barbs and hooks and squeezes out the sperm of previous males. Only after this is done is the sperm released. [Source: Jennifer Ackerman, National Geographic, April 2006]

Sex is often rough and occasionally fatal. Males have claspers at the end of their abdomens that they use to clasp a special plate on the female’s thorax behind her head. Males often clasp and have sex with the females during mid flight. Some species engages in heavy thrusting. The vise-like claspers of some species pierce the female’s heads.

Most females have sex with more than one partner. After sex the males of some species drag the female around to prevent her from being inseminated by other males. In other species, males kidnap and rape the females they find basking in the sun. Among other species, males attack copulating couples, bite them both and steal away the female. Others attack the female while she is laying eggs, drowning here in the process.

Dark Wing Patches on Dragonfly Males — Indicator of Climate Change?

Kati Moore wrote in Natural History magazine: Dark markings on dragonfly wings are a sexually selected trait, but a new study shows how these markings vary based on environmental temperature, and how their evolution may allow dragonflies to adapt to warming over the next hundred years. [Source: Kati Moore, Natural History magazine, October 2021]

The darker a dragonfly’s wings are, the more heat it absorbs. For males, darker wings also attract more mates. In one of the first studies to look at climate’s impact on a sexually selected trait, a team of biologists led by Michael Moore of Washington University in St. Louis collected data from field guides and citizen science observations for 319 North American dragonfly species and found that males of species in colder climates have darker wings than those in warmer climates.

They found the same pattern within species, with males in colder areas having darker wings. Using more than 2,700 iNaturalist photos of ten widespread species from a fifteen-year period, the researchers found that within populations, males had darker wings in colder years. Previous research found that individual dragonflies did not develop lighter wings when raised in warmer temperatures, suggesting that adaptive differences between individuals are genetic. This means that natural or sexual selection can affect how light or dark, on average, males’ wings become over time.

Based on current predictions for global temperature increases and observed evolution of similar traits, the researchers calculated how much change in each dragonfly species’ wings markings can be expected by 2070, and whether it will be enough to keep species from going extinct. Their results suggest that male dragonflies’ wing pigmentation will decrease by about 6 percent on average, though some species will lose as much as 26 percent of their wing pigmentation. However, any changes in wing color are likely to be mediated by other pressures if, for example, such changes affect males’ ability to defend territories or find mates. In addition to refining these predictions, Moore said he hopes to further investigate factors affecting female wing coloration, as it does not respond to temperature the same way as male wing coloration. (PNAS)

Fireflies

Fireflies, or lightning bugs, are not flies. They are a kind of beetle that belong to their own family: Lampyridae (“shining ones”). There are about 2,000 different species, with about 200 in the United States alone. Different species flash in different ways. The flashmaking organ at the end of their abdomen is called a lantern. The flashing signals originate in the brain.

Fireflies emit light a an efficiency rate of 41 percent, compared to 30 percent for the LED (light-emitting diodes) — the most efficient man-made lights. Fireflies generate about 1/40th of a candle of light. They generally flash when they want sex. Like other bioluminescent creatures they combine oxygen, luciferin, and adenosine triphosphate (ATP) to produce light. ATP is a compound all plants and animals use for energy. Most food eaten by humans is converted to ATP. The signal to flash travels from the brain to the lantern using nerve cells that never touch the lantern and molecules of nitric oxide that travels through cell membranes to the lantern. Nitric oxide is found in human brain but is different from nitrous oxide ("laughing gas").

According to Natural History magazine: Attractive as they are to humans, fireflies are surprisingly repugnant to other insect-eating creatures. Researchers have found that birds, lizards, bats, toads, and mice will avoid dining on fireflies once they’ve sampled a few. Fireflies not only smell and taste terrible (according to some adventurous entomologists) but are loaded with toxic steroids, a feature that’s helped them survive for ages despite their habit of advertising their presence so luminously on summer evenings.

Firefly Flashing

It mostly males that do the flashing. They fly around the air, occasionally flashing, trying to attract the attention of females who are usually sitting stationary on the ground or on a bush. If a female responds with a blink or two she is telling the male she is interested enough to let him come and check her out.

Sometimes males have difficulty locating the females. Sometimes the females don’t flash back. Research indicates that females of some species prefer males that can flash longer and faster. Sometimes the response light is a ruse from a deadly larger species trying to attract a meal. When the male flies down to investigate he is devoured by the imposters who sometimes need the chemicals to ward off things that might eat it.

Fireflies spend years underground as larvae, eating earthworms, snails, and other insects. There emerge for only a week or two. Their only mission is reproduce before they die. More than half of the males fail to mate. In temperate climates a wet spring often foretells a summer with lots of lightning bugs. Wet soil is thought to be good for both the fireflies and the things they eat.

According to Natural History magazine: During the two weeks that they live as adults they do not eat — males flit back and forth signaling their fitness in species — specific blinks, and females reply with flashes to indicate availability. As many as twenty males, responding to the seductive call, may pile on a hapless female in hopes of siring her brood. Eventually, a pair hooks up, copulating sometimes until dawn, after which the female crawls away to lay her eggs, while males, especially those unsuccessful in love, continue on until they run out of the energy reserves they accumulated as larvae.

Each species has distinctive flashing and flying patterns. The Big Dipper firefly, one of the most common in the Washington D.C. area, give a long flash while flying in a “J” pattern. “Photinus macdermotto” flies straight and slow, flashing twice every six seconds. Some flash are like Morse-code dot-and-dash messages.

Endangered Fireflies

According to Reuters: Fireflies, may soon blink out. Fourteen of 128 firefly species — which make up a family within the beetle order — are threatened in the U.S. and Canada, according to the conservation group Xerces Society. Urban light pollution, thought to be partially responsible, can confuse fireflies, which rely on their own nighttime bioluminescence to attract mates and repel predators. [Source Julia Janicki, Gloria Dickie, Simon Scarr and Jitesh Chowdhury, Reuters. December 6, 2022]

In the United States there are concerns that firefly populations have been hurt by lawn pesticides, concrete sprawl and the capture of the insects for their chemicals which are used in scientific research.

Humans who catch fireflies and put them in a jar are advised to make sure there are air holes and a damp piece of paper in the jar. They should be set free the following morning. Some people have had success using a penlight to attract females. One man who has had success doing this told the Washington Post, “You can convince the firefly that there’s female there so he’ll get close, and he’ll do it again.”

Image Sources: Wikimedia Commons

Text Sources: Mostly National Geographic articles. Also 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 December 2024