What Are Big Flies Called? Common Types & Names

When people refer to “big flies,” they are often describing a variety of larger insect species that can differ significantly in their characteristics and behaviors. This article explores some of the most commonly encountered larger flies and their distinguishing attributes, helping to identify them and appreciate their role in various environments.

Common Giants of the Fly World

Horse flies are robust insects, typically 0.5 to 1.25 inches (12 to 32 mm) long. Females are known for their painful bites, as they require blood meals for reproduction, while males primarily feed on nectar. These flies often have large compound eyes, with some species displaying colorful purple or green bands. Their mouthparts are strong and blade-like, adapted for cutting skin to access blood.

Blow flies are large flies, 7 to 16 mm (0.28 to 0.63 inches) long. Many species exhibit a metallic sheen, appearing in shades of blue, green, or black. They commonly lay their eggs on decaying organic matter, including animal carcasses.

Bot flies are chunky, often bee-like, with adults typically measuring 12 to 19 mm (0.5 to 0.75 inches) long. They may be black with pale yellow markings. Adult bot flies generally do not feed, as their larvae are parasitic and develop within mammal tissues.

Crane flies, sometimes mistaken for oversized mosquitoes, are slender insects with exceptionally long legs, ranging from 7 to 35 mm (0.25 to 1.5 inches) in body length. Most adult crane flies do not possess biting mouthparts and generally do not feed.

Cluster flies are slightly larger than common house flies, typically around 5/16 inch (7.9 mm) long, and are dark gray with golden hairs on their thorax. Unlike many other flies, cluster flies are known for their sluggish movement and often seek shelter indoors to overwinter, congregating in large numbers. Their larvae develop in the soil, feeding on earthworms.

Key Characteristics of Large Flies

Large flies share several defining physical characteristics within their insect order. Their bodies are generally robust, built for efficient flight. A distinguishing feature of all true flies is the presence of only one pair of functional wings, located on the mesothorax. The hind wings are modified into small, club-shaped structures called halteres, which vibrate during flight and function as gyroscopic stabilizers, aiding in balance and maneuverability.

Another prominent characteristic is their large compound eyes, which often cover a significant portion of the head. These eyes are composed of thousands of individual visual units called ommatidia, enabling flies to detect even slight movements over a wide field of view. Some large flies, like horse flies, may have eyes with distinct colorful bands.

The mouthparts of large flies are adapted for consuming liquid diets, though their specific structures vary depending on feeding habits. For instance, horse flies possess piercing and slicing mouthparts to obtain blood. Conversely, flies such as blow flies and house flies have sponging or lapping mouthparts, designed for consuming liquid substances from decaying organic matter. Some adult bot flies have non-functional mouthparts, relying on nutrients acquired during their larval stage.

Understanding Their Place: Scientific Categories

All true flies, including the larger species, belong to the insect order Diptera. The name “Diptera” originates from Greek words, with “di” meaning “two” and “ptera” meaning “wings,” directly referencing their defining characteristic of having only a single pair of functional wings. This two-winged nature is a key feature that differentiates true flies from other insects that might have “fly” in their common names, such as dragonflies or butterflies, which possess two pairs of wings.

Within the order Diptera, numerous families encompass the diverse range of flies, including those considered “big.” This classification system helps scientists organize the vast number of fly species and understand their evolutionary relationships.