Fly

A fly (pl. flies) is an insect of the order Diptera (from Ancient Greek δι- di- 'two' and πτερόν pteron 'wing'), named for the single pair of wings. The hindwings have changed into halteres, organs that help flies control their flight. Diptera is a large group with more than 150,000 species, including horse-flies, crane flies, hoverflies, mosquitoes, and others.

Flies have a mobile head, with large compound eyes, and mouthparts for sucking liquids. Their wings help them fly easily, and claws on their feet let them stick to smooth surfaces.

Diptera is an important insect order for nature and people. Flies help plants grow by moving pollen, after bees and their Hymenopteran relatives. Fruit flies are used in science to learn about living things, but mosquitoes can spread diseases like malaria and dengue.

Taxonomy and phylogeny

Dipterans, or true flies, are holometabolous — this means they change a lot during their life cycle. They belong to a group called Mecopterida, which also includes insects like Mecoptera, Siphonaptera, Lepidoptera and Trichoptera. What makes most true flies special is that they have just one pair of wings, unlike other insects that might have “fly” in their names but actually have two pairs. Some true flies, like louse flies, have even lost their second pair of wings.

Flies have been around since the Middle Triassic period, about 240 million years ago, and became very common during the Middle and Late Triassic. Early flies probably did not eat nectar from flowers — flowers didn’t exist yet! Instead, scientists think they might have eaten honeydew, a sweet liquid made by bugs that suck sap from plants. Flies’ mouthparts are perfect for lapping up such sticky drops. Over time, flies evolved in three big bursts, with many new species appearing in the Triassic, Jurassic, and Paleogene periods.

Flies live almost everywhere on land and are very numerous. Well-known flies include house flies, blow flies, mosquitoes, gnats, black flies, midges, and fruit flies. Over 150,000 species of flies have been officially named, and there are probably many more waiting to be discovered. Some flies, like mosquitoes and crane flies, have long, thin bodies and antennae, while others, like house flies, have shorter bodies and antennae. Many fly larvae grow in water, and some can survive in very harsh places — from glaciers to hot springs! Adult hoverflies are famous for looking like bees or wasps to stay safe from predators.

Anatomy and morphology

Flies are insects made for flying. Their bodies have three main parts: the head, the thorax, and the abdomen. The head has large, round eyes and antennas to sense their surroundings. Flies have one pair of wings on the thorax and smaller balancing organs called halteres to help them stay steady while flying.

Flies can move quickly and change directions fast because of their special wings and halteres. They often fly straight and then quickly turn. Some flies fly high, while others stay near the ground. Their bodies help them fly well and avoid danger.

Life cycle and development

Flies change in four stages: egg, larva, pupa, and adult. The larva stage can last a long time, while adult flies live shorter lives. Adult flies focus on finding mates and laying eggs. Many fly larvae grow in safe spots like water, rotting fruit, or inside other animals. These larvae have soft bodies and can dry out if they are in air.

When flies become pupae, they change in different ways. Some pupae show parts of the adult fly, while others are inside a hard shell. The adult fly's main job is to reproduce. They can do this quickly, which helps flies increase in number during mating season.

Ecology

Flies, also called dipterans, are found everywhere and have many important jobs in nature. Their babies, called larvae, can eat plants, dead things, or even live inside other animals. Some fly babies live in water, and others live on land. Adult flies usually drink nectar or other liquids.

Flies have many ways to stay safe from animals that might want to eat them. Some flies look like bees or wasps to scare away attackers. Others live inside ant nests and smell like ants. Even though flies face many predators like birds, bats, and spiders, they have smart tricks to help them survive.

Human interaction and cultural depictions

Flies have been important in many cultures, both good and bad. In Navajo beliefs, Big Fly is a special spirit. In Christian demonology, Beelzebub is known as the "Lord of the Flies" and linked to the Philistines.

Flies appear in stories from long ago. In ancient Sumer, a fly helped the goddess Inanna when her husband Dumuzid was in danger. In Egypt, flies were given to brave soldiers and were thought to carry the souls of people who had passed away.

Some flies help control pests by eating other insects. Others, like mosquitoes, can spread sickness, but many flies are important for breaking down dead material and keeping the environment clean. Scientists study a special fly called Drosophila melanogaster to learn about genes and how living things grow and change.