AbstractA total of 2,545 specimens of scatopsids were collected by the BioSCAN project in Los Angeles, California, United States—an urban biodiversity project that worked with citizen scientists managing Malaise traps during 108 wk between September 2013 and October 2016. This is one of the largest collections of minute scavenger flies (Diptera: Scatopsidae) ever reported from a single project. Eleven species were identified: in the Ectaetiinae, Ectaetia betzi sp.nov.; in the Psectrosciarinae, Psectrosciara gonzalezae sp.nov.; in the Scatopsinae–Scatopsini, Scatopse notata (Linnaeus); in the Scatopsinae Colobostematini, Holoplagia guamensis (Johannsen); in the Scatopsinae Swammerdamellini, Aztecatopse huertai sp.nov., Swammerdamella marginata (Cook), Coboldia fuscipes (Meigen), Quateiella quatei (Cook), Abrhexosa grossa (Cook), Abrhexosa ryckmani (Cook), and Cooka melanderi (Cook). The three new species are described and illustrated. Phenology of the species collected is discussed. Of the species collected, Scatopse notata, Holoplagia guamensis and Coboldia fuscipes are widespread, cosmopolitan species. Previous records from southern California suggest that eight other species may exist in the area and were not collected—two of Psectrosciara Enderlein, two of Rhegmoclemina Enderlein, and at least one species of Parascatopse Cook, Apiloscatopse Cook, Colobostema Enderlein, and Akorhexoza Cook. This article documents for the first time the genus Aztecatopse Haenni and Huerta in United States and Holoplagia guamensis in continental United States. Overall, the Los Angeles conurbation has been able to keep over 55% of the expected diversity of the family in the area, and some actions in urban planning could possibly extend considerably this percentage. This study emphasizes the value not only of sampling for insect biodiversity in urban environments but of the role of community (=citizen) science in expanding the breadth of such sampling efforts.