The staff in the Division of Invertebrate Zoology study and archive the living non-vertebrate animals, which make up 95% of all animal species. The Division houses more than 24 million specimens, which comprises about 500,000 species. Most of these specimens are terrestrial arthropods, but there are large collections of marine and freshwater invertebrates. Strengths of the collections reflect the research of current and past curators: Arachnids (especially spiders and scorpions), aculeate (sting-bearing) Hymenoptera (including bees, wasps and ants), gall wasps (Cynipoidea), certain Diptera (especially Drosophilidae, Syrphidae and Tachinidae), Hemiptera, Isoptera (termites) and their symbiotic protists, macro-Lepidoptera (particularly of the New World), rove beetles (Staphylinidae), the primitively wingless insects (bristletails and silverfish), marine Mollusca, and fossils in amber. Research centers around field exploration, the collections, and laboratory studies using morphology and DNA sequences to examine the evolutionary relationships of a spectrum of groups from species to phyla.