Several kinds of nonbiting flies can be found in and around farms, residences, and food-handling establishments. These flies cause annoyance and discomfort and can also be harmful to human and animal health. All filth flies have an egg, larva (maggot), pupa, and adult stage in their life cycle. The adult fly has two major wings and two reduced wings, called halteres. These reduced wings are knob-shaped balancing organs.
This Daring Fly Swims in a Shimmering Bubble Shield
Covered in a shiny bubble, the alkali fly scuba dives into the harsh waters of California’s Mono Lake. Thanks to an abundance of hair and water-repellent wax, this remarkable insect remains dry while embarking on a quest for tasty algae and a place to lay its eggs.
This fly is the Jacques Cousteau of flies. It dives where no other insect dares, in its very own scuba gear.
It risks it all for food and a place to lay its eggs.
The alkali fly thrives in waters three times saltier than the ocean, here in California’s Mono Lake.
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It lives among these otherworldly towers of limestone deposits called tufas.
Those same minerals make the water inhospitable for almost every other form of life. Like if someone made a soup of table salt, baking soda, and soda ash, an abrasive stain remover.
But the alkali fly? It loves it. Scientists call this kind of creature an extremophile. It survives in an extreme environment.
As a larva, it spends all its time underwater. It gets oxygen through its skin.
These special kidneys, called lime glands, pump excess salts out of its body. It’s a process called osmoregulation.
When it grows up, it gets its wings, but it loses those lime glands and can’t breathe under the surface.
So this extremophile employs an extreme solution: a shimmering bubble shield enclosing its entire body.
The only things sticking out are its eyes … and its claws.
As it dives from the surface, it captures air between its body and hairs, like its very own oxygen tank. And the fly isn’t actually getting wet.
It can do this thanks to its charming looks. It’s far hairier than your average fly.
Check out its shaggy wings, fluffy legs, and bristly abdomen.
These hairs, and the fly’s body, are covered in water-repellent wax. It’s a lot of product, but these waxy hairs are crucial to the fly’s survival.
Here’s an animal that doesn’t have as many hairs: This red ant wandered too close to the lake’s edge. Now, it can handle some amount of freshwater, but the mineral-rich Mono Lake water bogs it down.
Mono Lake’s water is some of the wettest water in the world. Yeah, you heard me right.
You see, all water sticks to itself; that’s why rain comes down in neat droplets. But the minerals in Mono Lake water make it even stickier. It feels slippery and soapy.
Check out the wing of this house fly when it touches a droplet of pure water. The wing pulls away from the drop easily. But when it touches water with the same compounds as Mono Lake? It sticks.
So your standard fly, frog, even fish avoids the lake at all costs.
The only other life down here is brine shrimp and one type of microscopic worm. That leaves nearly all the delicious algae for the alkali fly.
The fly sticks out its proboscis and slurps it up where the algae collects on tufas.
But this diving fly is not invincible. The water levels of Mono Lake are getting lower. We divert water from the streams that feed the lake, and rising temperatures mean it’s drying up faster than before.
This makes the lake more salty, and those larvae that spend their days underwater can only handle so much. Fewer of them are growing into adults.
Maybe you’re thinking, “So what, it’s just a few flies!” But these swarms help feed millions of birds as they migrate across the Americas.
While the alkali fly may seem audacious, even indestructible, it still relies on a delicate balance to survive.
Hey, Deep peeps, want to learn more about Mono Lake’s world-famous tufa towers?
Head over to PBS Terra’s new science show, Untold Earth. You’ll uncover the lake’s primordial secrets, and meet the people working to save it for future generations. See you there!
House Fly
The house fly (Figure 1) is one of the most common of all insects. It is worldwide in distribution and is a pest in homes, barns, poultry houses, food-processing plants, dairies, and recreation areas. It has a tremendous breeding potential, and during the warmer months can produce a generation in less than two weeks. In many areas of Florida the house fly breeds continually throughout the year.
House fly eggs are laid in almost any type of warm organic material. Animal or poultry manure is an excellent breeding medium. Fermenting vegetation such as grass clippings and garbage can also provide a medium for fly breeding. The whitish eggs, which are laid in clusters of 75 to 100, hatch within 24 hours into tiny larvae, or maggots. In four to six days the larvae migrate to drier portions of the breeding medium and pupate. The pupa stage may vary in length considerably, but in warm weather can be about three days. When the adult emerges from the pupal case, or puparium, the wings are folded in tight pads.
The house fly crawls about rapidly while the wings unfold and the body dries and hardens. Under normal conditions this may take as little as an hour. Mating occurs immediately. A house fly may go through an entire life cycle—egg, larva, pupa to winged adult—in six to 10 days under Florida conditions. An adult house fly may live an average of 30 days. During warm weather two or more generations may be produced per month. Because of this rapid rate of development and the large numbers of eggs produced by the female, large populations build up.
House flies are strong fliers and can become widely distributed by flying, wind currents, vehicles, and animals. Generally, however, flies are abundant in the immediate vicinity of their breeding site. Under certain conditions, they may migrate one to four miles, but are usually limited to one-half to two miles.
House flies feed by using sponging-type mouthparts. As the fly moves about from one food source to another, it samples and eats its food by regurgitating liquid and dropping it on the food to liquefy it. Light-colored spots called fly specks are visible signs of this type of feeding. Darker fly specks associated with house flies are fecal spots.
The house fly’s feeding and breeding habits, along with its persistence for invading homes and feeding on human food, enable the house fly to spread many intestinal diseases such as dysentery and diarrhea.
Resistance to insecticide is a complex problem associated with chemical control of insects. Recognized some more than 75 years ago, it is not a new problem. Resistance is the ability of an insect population to withstand exposure to insecticides, and this is acquired by breeding among insects that have survived previous exposures to an insecticide that did not wipe out the whole population. The surviving insects are resistant either because biochemical mechanisms (enzymes) enable them to quickly break down the insecticide or behavioral adaptations enable them to somehow avoid the insecticide.
Flesh Flies
Flesh flies (Figure 2) are a scavenger fly species that usually feeds on carrion or meat scraps in garbage. They are medium-to-large flies and usually have three dark thoracic stripes and a mottled abdomen. Many of the common species have a red tip on the abdomen.
Female flesh flies retain their eggs within their body until they are ready to hatch. The larvae are deposited directly onto the food the immature will be eating. The life cycle for the common species can be completed in eight to 21 days.
The preferred breeding media around residences are decayed flesh, spoiling meat, and manure. Usually garbage cans, meat scraps, and dog food left outside are abundant sources of flesh fly breeding. Flesh flies can breed in dead rodents and birds in attics or wall voids of houses.
Blow Flies and Bottle Flies
There are quite a few species of blow flies (Figure 3) and bottle flies (Figure 4) that are found in and around residences. The green bottle flies, blue bottle flies, and bronze bottle flies are particularly abundant in Florida. In urban areas these flies may be more abundant than house flies.
The blow flies and bottle flies usually have a metallic blue, green, or both colors on the thorax and abdomen. These flies are strong fliers and range many miles from breeding places. They are abundant during the warm summer months.
Blow flies and bottle flies can breed on dead rodents and birds in attics or wall voids of houses. They usually breed in meat scraps, animal excrement, and decaying animal matter around houses. The adult flies are quite active inside and are strongly attracted to light. The mature larvae are often a problem when they migrate from breeding areas to pupate.
Blow flies usually lay eggs on dead animals or decaying meat. Garbage cans have been known to produce 30,000 blow flies in one week. The life cycle usually lasts nine to 21 days from egg to adult.
UFO? Flying Ship? No—It’s Nature’s Coolest Optical Phenomenon
A viral roadside photograph from a puzzled New Zealand resident shows a kind of optical phenomenon called a fata morgana.
What’s going on here? A ship appears to hover in the air just above the horizon. But that’s already a clue, because the narrow band around the horizon is home to some wild optical illusions.
The sun appears to squash into an oval or even into discrete rectangular bands. The moon looks notably larger than at other positions in the sky. Sometimes, you can still see a ship that has dipped below the horizon.
Here’s where some keen-eyed (and pedantic) people are sitting up in their chairs and saying, “These are phenomena, not illusions.” They’re not wrong! An optical illusion is something like the Hermann grid, where our eyes imagine and “see” something that truly isn’t there. An optical phenomenon is just something surprising that’s indeed actually happening.
You could never take a picture of your experience of viewing the Hermann grid, but you can photograph a mirage or a fata morgana. (The moon illusion really is an illusion, with no measurable change in visible size at the horizon.) From true optical illusions like the Hermann grid, we can note and reflect on the idea that our brains are communicating incomplete information to us—a lesson that’s humbling in a good way.
But optical phenomena may fill us with awe or even fear because of how alien they appear. Sometimes that’s literally alien, because fata morgana could pass for a flying saucer to someone in the right frame of mind. Let’s look at what causes this startling phenomenon. It’s a combination of two other phenomena called superior and inferior mirage.
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The optical phenomenon where you still see a ship that has traveled beyond the horizon is called a superior image, where you see as though from a higher position than you really have. A layer of warm air sits above a layer of cold air, and the difference bends light into your field of vision. It’s like having one of those round convenience store mirrors, and in the mirror you see the faraway ship.
Inferior mirage is the natural opposite. Cold air sits on top of warm air, and this bends the light downward. When you drive on a hot day and see mirage “puddles” on the pavement, that’s basically a repeated image of the sky that’s bent into a visible spot on the ground. It only looks like liquid because of the context: The sky isn’t on the ground, the same way the wavy sunset never looks like it’s really water.
More Optical Illusions
A fata morgana is a layer cake of both kinds of optical phenomena. Alternating bands of hot and cold air create several different bands where superior and inferior mirages meet. The effect is kind of like a rolling shutter photo, or the illusion collage where you cut strips of two photos and then alternate them.
Looking at these images feels confusing because of the way context is changed and removed—but nothing out of this world is going on at all.
Caroline Delbert is a writer, avid reader, and contributing editor at Pop Mech. She’s also an enthusiast of just about everything. Her favorite topics include nuclear energy, cosmology, math of everyday things, and the philosophy of it all.
