This chapter of the book "An Introduction to the Study of Insects" provides a comprehensive overview of various families within the order Diptera ( flies ), focusing on their identification and characteristics. The text covers a wide range of fly families, including Otitidae, Trypetidae, Lonchaeidae, Pallopteridae, Lauxaniidae, Tanypézidae, Micropézidae, Neridae, Sépsidae, Piophilidae, Diópsidae, Clusiidae, Sciomyzidae, Dryomyzidae, Periscelidae, Coelopidae, Heleomyzidae, Chyromyidae, Psílidae, Anthomyzidae, Tethinidae, Opomyzidae, Ochthiphilidae, Agromyzidae, Phylomyzidae, and Drosophilidae. Each family is described with specific characteristics, such as wing venation, antennae, legs, and chaetotaxy (bristles arrangement). The chapter also includes detailed illustrations and diagrams to aid in the identification of these flies. Additionally, it provides practical information on rearing and culturing flies, particularly Drosophila melanogaster, which is widely used in genetic studies due to its short life cycle and ease of culture. The text concludes with references to resources for further study, including books and journals on entomology and insect rearing.This chapter of the book "An Introduction to the Study of Insects" provides a comprehensive overview of various families within the order Diptera ( flies ), focusing on their identification and characteristics. The text covers a wide range of fly families, including Otitidae, Trypetidae, Lonchaeidae, Pallopteridae, Lauxaniidae, Tanypézidae, Micropézidae, Neridae, Sépsidae, Piophilidae, Diópsidae, Clusiidae, Sciomyzidae, Dryomyzidae, Periscelidae, Coelopidae, Heleomyzidae, Chyromyidae, Psílidae, Anthomyzidae, Tethinidae, Opomyzidae, Ochthiphilidae, Agromyzidae, Phylomyzidae, and Drosophilidae. Each family is described with specific characteristics, such as wing venation, antennae, legs, and chaetotaxy (bristles arrangement). The chapter also includes detailed illustrations and diagrams to aid in the identification of these flies. Additionally, it provides practical information on rearing and culturing flies, particularly Drosophila melanogaster, which is widely used in genetic studies due to its short life cycle and ease of culture. The text concludes with references to resources for further study, including books and journals on entomology and insect rearing.