flys

Flies are insects in the order Diptera. The correct plural is flies; flys is commonly considered a misspelling. Diptera is a large and diverse group with about 120,000 described species found worldwide. Adults typically have one pair of wings, while the hind wings are reduced to small balancing structures called halteres that help with flight stability. The group includes familiar forms such as house flies, fruit flies, mosquitoes, crane flies, and many others in a wide range of sizes and shapes.

Life cycle and development are holometabolous, meaning flies undergo complete metamorphosis: egg, larva, pupa, and adult. Eggs are laid on or near suitable food sources, such as decaying organic matter, animal waste, or plant fluids. Larvae, often called maggots, are usually legless and adapted to their particular diet. Pupation occurs in soil, water, or within the food substrate, after which the winged adult emerges.

Ecology and behavior vary widely among species. Adults may feed on nectar, plant sap, or animal blood, while larvae frequently occupy aquatic, semi-aquatic, or terrestrial habitats linked to detritus or living tissue. Flies play critical roles in ecosystems as decomposers, pollinators, and food for other animals. They are also used in scientific research, notably Drosophila melanogaster as a model organism, and some blowflies are important in forensic science.

Human relevance is mixed. Several species are disease vectors (such as mosquitoes that transmit malaria, dengue, and Zika), others are agricultural or domestic pests. Conversely, flies contribute to nutrient cycling, biological control, pollination, and biomedical research.