Fly

Flies are small flying insects belonging to the order Diptera distinguished by a mobile head, two large compound eyes, a single pair of flying-wings, and an appendage-like structure used for sucking. They exhibit excellent species diversity and are abundant almost in all parts of the world.

Physical Description and Appearance

Size: Their size varies depending on the species. Adult houseflies, for example, are 0.24-0.28 in (6-7 mm) long while blowflies measure 0.3-0.4 in (8-10 mm). The largest fly species in the world is Gauromydas heros, measuring up to 2.8 in (7 cm).

Body: They have a small, streamlined body with three segments – the head, thorax, and abdomen.

Head: Their head is mobile, bearing a pair of antennae, two large compound eyes and three simple eyes, and the mouthparts that include the maxilla, mandible, labium, and labrum.

Wings: Flies possess a pair of fore wings attached to their mesothorax, and they use these for flying. They also have two reduced hind wings (called halteres) on the posterior end of thorax.

Abdomen: It contains 11 segments, with the last two or three being adapted for reproduction.

Distribution

Flies are found in all the continents except for Antarctica. It is estimated that about 19,000 fly species exist in Europe while 20,000 species live in the sub-Saharan Africa, eastern and southern parts of the Arabian Peninsula, southwestern Pakistan, southern Iran, and Madagascar. About 22,000 fly species are found in North America, 23,000 in eastern India and Southeast Asia, and 19,000 in Australasia.

What kinds of Habitats do they live in

Flies are found almost anywhere, with the larvae commonly inhabiting damp places. Fly populations are typically the largest in humid areas.

How long do they live

Flies are mostly short-lived, and their lifespan varies depending on the species. On average, larger fly species, including houseflies, live for about 20-30 days while adult female mosquitos have a life expectancy of 42-56 days.

What do they eat

Flies are omnivores that feed on fruits, vegetables, meat, plant and animal secretions, and decaying organic material. Their diet also includes grass, nectar from flowers, and other insects. Horseflies, deer flies, and mosquitos feed on the blood of other animals.

Behavior

• Flies are generally attracted to food and rotting organic materials. Species like fruit flies and houseflies invade homes and restaurants, laying eggs in spoiled food and animal wastes.
• They undergo complete metamorphosis, with larvae emerging from eggs and developing into pupae, which then transform into adult flies.
• Flies usually fly on a straight path, making swift changes in direction and then flying again in a straight line. These directional changes, termed as saccades, are achieved within 50 milliseconds.
• They live and fly near the ground, although some flies like the Oscinella are dispersed by winds over vast distances and at heights of up to 2000 ft.
• The male flies in several species like the fruit flies, bee flies, and hoverflies defend their territories and chase intruding males or members of other species.

Adaptations

• The hindwings of flies, modified into halteres, allow them to perform different maneuvers during flight while helping them in balancing and guiding themselves.
• They have specialized chemoreceptors in their antennae, maxillae, pharynx, labium, feet, and wing margins for detecting smell and taste. The mechanoreceptors, on the other hand, are used for responding to touch.
• Many fly species like the hoverfly and fruit flies have developed mimetic resemblances for protecting themselves against predators. Hoverflies imitate bees and wasps while the fruit flies resemble spiders.
• Special sensory structures in certain blood-sucking species like horse flies and deer flies help in detecting infrared emissions and then move toward the target.

How do they Reproduce and Mate

Mating starts when a male fly approaches the female, after which he jumps towards her and mounts her. The female pushes her tubular ovipositor into the male genital opening to obtain sperm. The mating process lasts anywhere from half an hour to 2 hours.

A study has shown that male flies can produce a lesser amount of protein in the seminal fluid and manipulate their female partners to enhance their chances in reproductive competition.

Females are capable of laying up to 400-500 eggs in batches of 75-100 eggs over 3-4 days. In warm, humid weather, the eggs hatch in 12-24 hours.

Fly-FAQs

Interesting Facts

• Flies have quick reflexes that help them in escaping from predators, but their flight speeds are relatively slow.
• They can mate more quickly and effectively than most insect species.
• The fly larvae do not have any jointed “true legs”, but some species like the Tabanidae, Vermileonidae, and Simuliidae possess small, fleshy stub structures (prolegs) for holding onto prey or host tissues.
• At all the stages of their development, flies are eaten by animals like birds, frogs, bats, dragonflies, spiders, and lizards.
• Flies can have a negative effect on the environment. Species such as fruit flies, leaf-miner flies, and gall midges are pests for food crops, while others like screwworm, tsetse flies, and botflies attack livestock and spread disease.