The biodiversity of human dwellings: A dataset of nearly 24,000 observations of indoor life in the United States and Canada

This dataset ("NHA_indoor_organisms.csv") contains 23,782 records of nearly 2,100 species observed inside homes, offices, schools, and other indoor spaces in the United States and Canada. These records were made by approximately 3,000 volunteers on the platform “iNaturalist.org” who photographed wild (i.e. not pets, not captive or cultivated) organisms observed indoors as part of the Never Home Alone citizen science project that we started in 2018. Organisms were observed between May 1996 and April 2024, though most records were made between 2018 and 2024. Each row in the dataset is a unique record of an organism observed indoors. Columns contain spatiotemporal information and taxonomic identification of the record as well as additional metadata about both the observer and the taxonomic expert who reviewed the observation. Records were made in every US state and Canadian province (though no data were submitted from the Canadian territories), with California, North Carolina, New York, Texas, and Massachusetts containing the most observations among states/provinces. The vast majority of records were insects (Class: Insecta; 60% of records), spiders (Order: Araneae; 30%), and chordates (Phylum: Chordata; 4%), though the database also contains indoor fungi, plants, annelids, mollusks, crustaceans, ciliates, and many other groups. The most common species (>200 observations each) were, in descending order, the Asian lady beetle (Harmonia axyridis (Pallas, 1773)), brown marmorated stink bug (Halyomorpha halys (Stål, 1855)), house centipede (Scutigera coleoptrata (Linnaeus, 1758)), varied carpet beetle (Anthrenus verbasci (Linnaeus, 1767)), long-bodied cellar spider (Pholcus phalangioides (Fuesslin, 1775)), triangulate combfoot spider (Steatoda triangulosa (Walckenaer, 1802)), bathroom moth fly (Clogmia albipunctata (Williston, 1893)), and Eastern parson spider (Herpyllus ecclesiasticus Hentz, 1832). Conversely, the dataset also contains 1,100 singletons—species that were only observed once indoors. The most common families were, in descending order, jumping spiders (Salticidae), comb-footed spiders (Theridiidae), cellar spiders (Pholcidae), skin beetles (Dermestidae), ants (Formicidae), stink bugs (Pentatomidae), lady beetles (Coccinellidae), stealthy ground spiders (Gnaphosidae), funnel weaver spiders (Agelenidae), and cutworm moths and allies (Noctuidae). This dataset represents the first continental-scale survey of indoor species based on verified photographic records, and it provides a unique resource for examining the ecology and biogeography of organisms associated with the built environment—an anthropogenic ecosystem that is now larger than some natural ecosystems. Note that this submission also contains an R script ("final_analyses.R") which generates tables and figures showing descriptive statistics and basic analyses of the dataset, including a spatial density map of observations, analyses of the most common species and families, and a histogram of observation dates.