Essig Museum of Entomology, Entomological museum at University of California, Berkeley, US.

The Essig Museum of Entomology is a research museum at the University of California, Berkeley, dedicated to terrestrial arthropods. Its holdings include over 5 million pinned specimens, plus microscope slide, alcohol-preserved, envelope and Riker mount collections. Named collections cover thrips, aphids, lice, fleas, mites, true bugs and parasitic flies.

The museum originated in the 1880s as part of UC Berkeley's University Museum and expanded significantly after becoming the California Insect Survey in 1939. This transformation enabled more systematic research and expanded collecting efforts across the state.

The collection serves as a central reference for understanding California's insect diversity and how populations shift due to environmental changes. Visitors can observe how researchers document these changes and why this work matters for the region.

The museum opens to the public only twice a year, on Cal Day and Darwin Day, so plan a visit around one of those events. Researchers and others needing access at other times should arrange it in advance with the collections staff. Check the museum's own pages for the current dates before travelling.

The museum's holdings include named specialist collections such as the Robert L. Usinger Heteroptera Collection, the Edward O. Essig Aphididae Collection and the Morris A. Stewart Siphonaptera Collection. Researchers are also working with citizen scientists to digitally catalogue eight major insect collections.