Patterns of episodic emergences of Discoderus LeConte, 1853 (Coleoptera: Carabidae: Harpalinae: Harpalini) in the southwestern United States are presented and discussed. Standardized ground beetle sampling through the National Ecological Observatory Network (NEON) in southern Arizona elucidates mass emergence events of members of Discoderus who exhibit large fluctuations in annual abundance. Although there are no previous quantitative reports of similar events, Discoderus abundance is shown to drive overall carabid abundance in at least one Arizona grassland habitat. Evidence from circumstantial collecting suggests Discoderus obsidianus Casey, 1914 emerged in large numbers in Arizona during the summer of 2022. Remarkably, despite the large number of individuals collected during this event, this beetle is relatively uncommon in insect collections. Taxonomic difficulties in this genus are discussed and images of type specimens are presented.