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Fly: Characteristics, Diet, Facts & More [Fact Sheet]

Flies, often seen as mere nuisances, are actually among the most common and diverse insects on the planet, playing essential roles in ecosystems worldwide. With over 120,000 species identified across various habitats, flies are masters of adaptation, capable of thriving in almost every environment.

From the pollination of crops to the decomposition of waste, their contributions are invaluable to both natural ecosystems and human economies. This article aims to shed light on the fascinating world of flies, exploring their classification, physical characteristics, behavior, and ecological significance.

Join us as we dive into the life of these ubiquitous insects, discovering the hidden complexities of their existence and the reasons why they deserve our attention and respect.

The Fly at a Glance


Class:Insecta (Insects)
Family:Varied (e.g., Muscidae, Calliphoridae, Tachinidae)
Species:Over 120,000 identified species

Essential Information

Average Size:0.08 – 0.6 inches (2 – 15 mm)
Average Weight:Not typically measured
Average Lifespan:Weeks to months, depending on species and conditions
Geographical Range:Worldwide
Conservation Status:Most species are not endangered; some are critical for ecosystem health

Species and Subspecies

The order Diptera, to which flies belong, encompasses an immense diversity of species and subspecies, adapted to a wide range of environments and lifestyles. Among these, several species are particularly noteworthy:

  • Musca domestica, the common housefly, is perhaps the most familiar to humans, found in nearly every human settlement around the globe.
  • Drosophila melanogaster, the fruit fly, is a key species in genetic research, offering invaluable insights into genetics and developmental biology.
  • Calliphoridae, or blowflies, are known for their metallic blue or green coloration and play crucial roles in the decomposition process, recycling nutrients back into the ecosystem.
  • Anopheles spp., mosquitoes (a type of fly), are infamous for spreading malaria and other diseases, highlighting the public health importance of certain fly species.

Each species and subspecies has evolved unique adaptations that enable them to exploit different ecological niches. From the deserts to the Arctic, flies have colonized virtually every corner of the Earth, showcasing their incredible versatility and survival skills.

Top view of a fly


Flies display a remarkable variety in physical appearance, ranging from the tiny, barely visible fruit flies to the larger, more robust horseflies.

They typically have bodies that are 0.08 to 0.6 inches (2 to 15 mm) in length, with a pair of wings that distinguishes them within the insect world—the name “Diptera” literally means “two wings.” Unlike other insects, flies have their second pair of wings reduced to halteres, which are small, club-shaped organs used for balance during flight.

Their coloration varies widely, from dull browns and blacks to vibrant greens and blues, often serving as camouflage or warning signals to predators. Flies possess compound eyes that offer a wide field of vision, essential for detecting movement and evading threats. Their mouthparts are adapted for their specific diets, with some capable of piercing and sucking, while others sponge or lap up their food.

Sexual dimorphism is present in many fly species, usually manifested in size differences, with females often being larger than males, especially when they are gravid (carrying eggs). Additionally, males may have larger or differently shaped eyes, used for spotting females during mating rituals.

Habitat and Distribution

Flies are ubiquitous and have adapted to live in nearly every habitat on Earth, from the driest deserts to the wettest rainforests, and from sea level to high mountain ranges. They are particularly abundant in areas rich in decaying organic matter, which provides food for their larvae, including forests, fields, farms, and even urban areas.

The geographical distribution of flies is worldwide, with certain species adapted to specific environmental conditions that limit their range. For example, some species are found only in tropical or subtropical regions, while others thrive in temperate zones or even in arctic and alpine environments.

Fly compound eyes


Flies exhibit a wide range of behaviors, tailored to their diverse lifestyles:

  • General Behavior: Most flies are diurnal and are most active during the warmer parts of the day when they can be seen foraging for food, mating, or laying eggs. Some species are attracted to artificial lights at night.
  • Social Structure: Flies are generally solitary, but some species may gather in large numbers where food sources are abundant, such as on carcasses, feces, or flowering plants.
  • Communication: Flies communicate primarily through chemical signals (pheromones) and visual cues. Mating dances and displays are common among many species, with males performing specific patterns of flight or displaying body colors and patterns to attract females.
  • Feeding: Adult flies have diverse feeding habits, including nectar, plant sap, blood, or decaying organic matter, depending on their species. Their larvae, often referred to as maggots, usually feed on decomposing organic material, although some are parasitic.

The behavior of flies is closely tied to their ecological roles, with their activities significantly impacting nutrient cycling, pollination, and the control of pest populations.

Diet and Feeding Behavior

The diet of flies varies widely across different species, reflecting their diverse ecological roles:

  • Herbivores: Some fly species, like the flower flies or hoverflies, primarily feed on nectar and pollen, playing a role in pollination.
  • Carnivores and Parasites: Certain flies, such as the larvae of the robber flies, prey on other insects. Some species are parasitic, laying their eggs inside or on other insects, which the larvae then consume from within.
  • Omnivores: Many flies, including the common housefly, have a varied diet that can include nectar, plant sap, animal secretions, and decaying organic matter. They are equipped with sponge-like mouthparts that allow them to soak up their food.
  • Scavengers: Species like blowflies are attracted to decaying animal flesh or organic waste, where they lay their eggs, and the emerging larvae feed on the decomposing material.

Flies exhibit specialized feeding behaviors adapted to their diets. For example, predatory and parasitic flies have sharp mouthparts for piercing, while scavengers and omnivores may have developed an ability to detect chemical signals from potential food sources over long distances.


Flies, at various stages of their life cycle, are preyed upon by a wide range of predators:

  • Birds: Many bird species feed on adult flies, catching them in flight or picking them off surfaces.
  • Amphibians and Reptiles: Frogs, toads, and some lizards consume significant numbers of flies, using their sticky tongues to snatch them from the air or ground.
  • Insects and Arachnids: Other insects, including other fly species, predatory beetles, dragonflies, and spiders, are significant predators of flies. The larvae, in particular, are vulnerable to predation by ground beetles and parasitic wasps.
  • Mammals: Bats are known to catch flies mid-air during their nocturnal flights, using echolocation to detect and intercept them.

The presence of flies serves as an essential link in food webs, supporting the survival of various predatory species and contributing to ecosystem health and balance.

Fly on moss

Reproduction and Life Cycle

Fly reproduction and life cycles can be complex, with significant variation among species:

  • Breeding Habits: Mating often involves elaborate rituals, including aerial displays, pheromone release, and acoustic signals in some species. Males typically compete for female attention, who then select mates based on these displays.
  • Egg-Laying: Females lay eggs in environments suited to the survival of their larvae, which varies greatly among species. For instance, some lay eggs in water, others in soil, on plants, or in decaying organic matter.
  • Life Cycle Stages: The fly life cycle includes four main stages: egg, larva (maggot), pupa, and adult. The larval stage is where most of the feeding occurs, with larvae often adapted to specific environmental conditions or food sources. Pupation may take place in a protective casing or buried in the substrate. The duration of each stage can vary widely depending on species and environmental conditions, with some flies capable of completing their life cycle in just a week, while others may take months.

Reproduction rates among flies can be incredibly high, with some species capable of laying hundreds of eggs over their lifetime. This rapid reproductive rate is one of the reasons flies can quickly colonize suitable habitats and why they can be challenging to control in agricultural and urban settings.

Conservation and Threats

The conservation status of flies varies greatly across the multitude of species within the order Diptera. While many fly species are abundant and not of conservation concern, others play such critical ecological roles—especially as pollinators and decomposers—that their decline could have significant repercussions on ecosystem health. Some species are indeed rare or endangered, often due to habitat loss, pollution, and climate change.

Conservation efforts for flies focus on habitat preservation and restoration, reducing pesticide use, and promoting biodiversity. Understanding the ecological roles of flies, including their interactions with other species and contributions to ecosystem services, is crucial for their conservation and the broader environmental conservation efforts.

Fun Facts

  1. Master Fliers: Flies are among the most skilled flyers in the insect world, capable of performing intricate aerial maneuvers, including hovering, thanks to their highly specialized wings.
  2. Decomposition Champions: Flies, particularly in their larval stage, play a crucial role in breaking down and recycling organic matter, speeding up the decomposition process and returning nutrients to the soil.
  3. Medical Helpers: Maggot therapy, using sterile larvae of certain fly species, is an effective method for cleaning non-healing wounds by eating dead tissue and promoting healing.
  4. Incredible Diversity: With over 120,000 known species, flies exhibit an astonishing variety of forms, behaviors, and ecological niches, making them one of the most diverse groups of animals on the planet.
  5. High-Speed Reproduction: Some fly species can go from egg to adult in just seven days, allowing populations to explode under the right conditions, which is why they can quickly become pests if not managed.

Frequently Asked Questions

What do flies eat?

Fly diets vary widely, including nectar, blood, decaying organic matter, and other insects, depending on the species.

Why do flies rub their hands together?

Flies are often seen rubbing their legs together to clean them. Their legs are covered in sensory hairs, and keeping these hairs clean is vital for tasting and feeling their environment.

Can flies really spread diseases?

Yes, flies can spread diseases due to their feeding and breeding habits, particularly species that frequent unsanitary conditions and then come into contact with human food and living spaces.

How long do flies live?

The lifespan of a fly varies by species, but many common flies live about a month in their adult form, though the entire life cycle from egg to adult may be shorter or longer depending on environmental conditions.

Are all flies pests?

While some flies are considered pests due to their role in spreading diseases and causing annoyance, many species play beneficial roles as pollinators, decomposers, and food sources for other wildlife, highlighting the complexity of their roles in ecosystems.

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