Can Flies Swim? A Detailed Look At Flies And Water

If you’ve ever sat by a lake on a hot summer day, you’ve probably noticed flies buzzing around near the water. Some of those flies may even land on the water’s surface. So it’s natural to wonder – can flies actually swim? The short answer is – not really.

Flies don’t have the adaptations needed to propel themselves through water like fish or other aquatic animals can. However, flies can maneuver across the surface of calm water in some limited ways. In this comprehensive article, we’ll take a close look at flies’ relationship with water and examine whether they truly have any swimming capabilities.

We’ll start by looking at flies’ basic anatomy and how it relates to moving through air versus water. Next, we’ll go over examples of flies interacting with water in nature. Then we’ll analyze the limited ways flies can maneuver across calm water surfaces.

We’ll also discuss flies’ hydrophobic bodies and how they can float. Finally, we’ll compare flies to other insects like water striders that are skilled at locomotion on water. By the end, you’ll have a thorough understanding of flies’ capabilities (and limitations) when it comes to traversing water.

Flies’ Anatomy and Locomotion

Flies have wings and legs that are specially adapted for flight and moving around in the air, not for swimming in water. Their wings are thin, lightweight, and designed for generating lift and propulsion through the air (1).

Meanwhile, their legs are spindly and made for grasping surfaces while walking or climbing, not for pushing through water (2).

Wings Provide Lift and Mobility in Air

A fly’s two wings are composed of a thin membranous material supported by hollow veins. This creates a large surface area relative to the fly’s body weight, allowing the wings to generate enough lift to keep the fly airborne (3).

The wings can beat up to 220 times per second, giving flies great aerial mobility and allowing them to take off vertically, hover, fly backwards, and change direction rapidly (4).

Legs Specialized for Walking, Grasping, Not Swimming

While useful on land, a fly’s legs and feet would be a hindrance trying to swim. Flies have six legs with tiny hairs and pads that help them cling to and walk on surfaces (5). There are no webbed feet or flippers to aid with propulsion in water.

In fact, the spindly legs and large surface area of the wings would cause a lot of drag and water resistance if submerged (6). So while flies can float and survive on the surface for a short time, they cannot truly swim under the water.

Flies lack anatomical adaptations that would enable effective swimming. Unlike aquatic insects or true water bugs, flies do not have streamlined bodies, webbed appendages, or waterproof exoskeletons that facilitate movement through water (7).

They also lack specialized breathing structures to extract oxygen from water.

Bodies Not Streamlined for Swimming

Flies have rounded, bulky bodies with large surface area wings – features suited for flight but not swimming. Without hydrodynamic, torpedo-shaped bodies tapering to points at both ends, flies experience substantial shape drag as they move through water (8).

Their large wings only compound this problem by adding surface area and wave drag. This makes it extremely inefficient for flies to propel themselves through water.

No Webbed Appendages for Propulsion

Flies lack webbed or flattened appendages which aquatic insects use to paddle and propel through water. While a fly’s feet can generate thrust on land, its spindly legs and unwebbed feet cannot physically push enough water backwards to generate meaningful forward propulsion while swimming (9).

Additionally, the hairy texture and small surface area of a fly’s legs and feet makes them largely ineffective for paddling. So flies must rely entirely on fragile wings and legs ill-suited for aquatic mobility.

Exoskeletons Allow Short-Term Water Resistance

A fly’s exoskeleton provides some degree of water resistance, which is why flies can float on the surface for a brief period without harm (10). However, compared to truly aquatic insects, flies’ exoskeletons are more permeable and much less durable when submerged for an extended time.

Most flies would experience loss of motor control, exhaustion, and eventual drowning if trapped under water too long.

So while flies can withstand a brief water exposure, they lack specialized physical traits for swimming effectively as aquatic bugs do. Their anatomy and locomotion abilities point to adaptation for life on land, not in water.

Flies’ Interactions with Water in Nature

Attracted to Shorelines and Wet Areas

Flies are often attracted to shorelines, wetlands, and other moist environments due to their need for water and suitable breeding conditions (1). Shorelines provide flies with access to water for drinking as well as wet soil or vegetation for laying eggs.

Some species like mosquitoes require standing water to breed. Other flies seek out moist decaying organic matter along shorelines to lay their eggs. Wetlands, marshes, and muddy shores offer ideal conditions for flies due to their abundance of moisture, vegetation, and wet soil (2).

Shorelines also draw flies in search of food sources. Flies feed on dead and decaying animals, plant material, and organic waste. Wet environments promote decay and contain a diversity of food sources that appeal to flies.

Shorelines may also attract flies due to the presence of animals and aquatic life like fish, birds, frogs, and turtles which the flies may feed on or parasitize.

In addition, flies gravitate to shorelines and wetlands to escape from the heat and dryness. The cooler, damper conditions provide flies with a more favorable habitat than hot, arid areas. The vegetation along shorelines also supplies shade and shelter for flies.

Can Become Trapped in Water Surfaces

While flies seek out water, they can sometimes become trapped in water surfaces due to the unique properties of water and flaws in their physiology (3). Flies have hydrophobic hairs on their body which normally repel water.

However, if these hairs become damaged or weighed down by moisture, flies can become waterlogged and stuck.

Another factor is water tension. The high surface tension of water often prevents lightweight insects like flies from breaking through the water’s surface once they touch down. The more a fly struggles, the more tangled it can become. Fly legs and wings may get wet, making it impossible to fly away.

Without self-grooming abilities, flies have no way to remove the water weighing them down.

Lastly, flies have poor underwater vision. Once trapped in water, they cannot see clearly enough to navigate and escape. Their natural instinct to fly works against them underwater as their wing movements only splash more water up onto their bodies.

While not all flies encountering water become trapped, these factors put them at high risk. Flies that accidentally fall into water bodies can ultimately exhaustion themselves and drown if they cannot reach dry land or vegetation.

This demonstrates the precarious and often deadly interaction flies can have with water surfaces.

Limited Maneuvering Abilities on Water

Using Surface Tension to Stay Afloat

Flies are able to float and maneuver on water to a certain extent by relying on surface tension. The high surface tension of water, coupled with the lightweight body and tiny foot size of flies, allows them to distribute their weight and avoid breaking the water’s surface (American Museum of Natural History).

Flies can skate across the surface of calm waters thanks to this physical phenomenon, though they cannot propel themselves purposefully.

When positioned properly, flies can remain buoyant on top of still water for hours at a time. Their waterproof exoskeleton and ability to trap air within their hairs also aids this limited aquabatic ability.

However, agitating the water or decreasing surface tension would cause flies to break through and become waterlogged.

Walking and Hopping Across Calm Water

On bodies of water with minimal waves or ripples, flies exhibit the capacity to walk and hop short distances. Their tiny feet and featherweight allows them to stand, move laterally, and make short hops without fully submerging.

According to an observational study, house flies were able to traverse up to 5 inches in this stilted, awkward manner (Proceedings of the Royal Society of London).

The limited mobility of flies on calm waters enables brief water crossing to reach food, mates, and other resources. However, lengthy distance travel or swimming is physically impossible for flies. Without the capacity for directed propulsion or stroke techniques, flies cannot overcome water’s drag for long distances.

While floating, flies remain stranded and at the mercy of wind or water currents. Their tiny leg strokes lack the power to steer themselves to shore. Thus, traversing water bodies is a risky endeavor for flies, albeit possible for short hops across very still surfaces.

Comparison to True Water-Walking Insects

Water Striders

Water striders are a type of insect that can actually walk on water. They have long, slender legs with tiny hairs that repel water, allowing them to float on the surface tension. Water striders use the surface of ponds, streams, and other calm bodies of water like a trampoline, skating and jumping rapidly across without sinking.

Amazingly, some water striders can even walk on moving water, using their quick reflexes to stay above the waves and ripples.

In contrast, flies cannot truly walk on water like water striders can. When flies land on water, they will eventually get waterlogged and sink if they do not take off again quickly. They rely on the surface tension to briefly stay on top, rather than having special adaptations for life aquatic life like water striders.

Other Aquatic Bugs

There are many other insects and bugs that have evolved impressive adaptations for life in the water.

• Giant water bugs have oar-like legs for swimming and breathing tubes called siphons that allow them to breathe underwater.
• Whirligig beetles have specially divided eyes that allow them to see above and below the water surface at the same time.
• Diving beetles trap air bubbles under their wings when diving underwater to breathe.
• Water scorpions have straw-like mouthparts to suck fluids from prey while hiding underwater.

Flies have no comparable specializations. They are designed for life in the air, not water. While flies can briefly float or skip along the water surface, they cannot truly walk on or live underwater like aquatic bugs.

Conclusion

As we’ve seen, flies don’t truly have the capacity to swim as we think of swimming in aquatic animals. Their anatomy is adapted for flying and terrestrial locomotion, not propulsion through water. However, flies can use the surface tension of calm waters to stay afloat and maneuver in limited ways, like hopping and walking short distances before becoming trapped.

While fascinating to witness, these behaviors don’t indicate true swimming abilities. In the end, flies are best suited to life on land, ideally near sources of standing water and moisture where they thrive.

Among insects, talents for swimming lie much more with water striders and other bugs anatomically adapted for aquatic environments.