The collection comprises around 1,300,000 specimens representing 27,000 species from all parts of the world with a focus on Europe. It includes 21,000 type specimens of 10,000 species descriptions. Approximately 1 million specimens are dry specimens mounted on pins. In addition, there are several thousand preparations embedded in a solid medium as well as numerous ethanol preparations – mainly dipterans from traps or larval stages and fleas (Siphonaptera).

With 150,000 described species, dipterans (flies and midges) are among the species-richest insect orders. There are about 10,000 species in Germany alone. This makes dipterans (alongside the similarly diverse order of hymenopterans) even the most comprehensive order of the animal kingdom.

The Siphonaptera (fleas) Collection comprises 1,200 specimens representing 237 species. It includes type material from 36 species descriptions. The dipterological part of the library consists of 1,200 books and brochures and a large collection of reprints.