The Diptera order is characterised by the presence of a single pair of wings. It includes mosquitoes, syrphid flies, horseflies and flies, amongst others. Accounting for 15% of all animal species in the world, 150,000 species have been counted, described and classified into 150 families.

The Diptera collection is divided into a general collection classified by family and separate nominal collections. The core collection thus consists of two historical nominal collections: the Meigen and Macquart collections, both dating from the 19th century; these alone include over 5,000 holotypes. The Diptera collection contains 2.5 million specimens, including 8,000 holotypes and around 30,000 species (or 20% of all known Diptera). All biogeographical regions are represented. The specimens are preserved dry, in alcohol or on microscope slides.

In 1919, Eugène Séguy was hired by the Muséum and took charge of a new section entirely dedicated to Diptera. Based on his own collection, various acquisitions and an impressive quantity of indeterminate specimens, he gradually built up a general collection which was added to the Meigen and Macquart collections. Later, he was also responsible for the addition of the Pandellé, Perris and Dufour collections to the Muséum. In the early 1950s, the Muséum’s Diptera collection eventually become one of the biggest in the world.

The Diptera collection is above all an aid to fundamental systematics research (taxonomy and phylogeny).
Moreover, as the biology of the Diptera is exceptionally diverse (there are predators, parasites, pollinators, phytophagous and hematophagous species, etc.), some diptera are major carriers of diseases (malaria, sleeping sickness, etc.) and others can be bred easily in the laboratory (Drosophila), many species are used as preferred research models in evolutionary biology, genetics, medical entomology and forensic entomology.

This Diptera collection often plays an essential role in many fundamental and applied research projects, so the Muséum welcomes many visiting researchers, mainly from abroad, as well as lending 2,000 to 3,000 specimens every year. The collection is managed by two researchers (C. Daugeron and V. Debat) and a technician (E. Delfosse). The computerisation and digitisation of the types in the Meigen and Macquart collections began in 2014 as part of the E-Recolnat project, and will continue until 2018. A technician (S. Verbeck) is in charge of the process.