Sixteen dead Ferocactus wislizeni (Engelm.) Britton & Rose (Cactaceae), known variously as fishhook barrel cactus, candy barrel cactus, or compass plant, were discovered in various states of decay near Portal, Arizona during July 2011. A survey of the Coleoptera in the rotting cacti resulted in the collection of 976 specimens representing 11 families and 35 species. Volume of cactus was significantly positively correlated with moisture content and moisture content was significantly positively correlated with species richness and abundance. Findings indicated that there may be three distinct successional stages—wet (saturated), moist, and dry—during cactus late decomposition. A review of literature listing species collected from decaying cacti and succulents is provided with updated nomenclature. Photographs and basic biological information are provided for 20 taxa of interest and relevant literature containing descriptions, keys, distributional data, and biological/life history data is reviewed.