Most people live with arthropods in their homes. It would be exceptional to find a home with not even a stray fruit fly. Leong and colleagues* investigated the arthropods found in homes and identified factors that correlated with the number taxa found (family level). They found that the numbers increased with the size of the house, the amount and diversity of the ground cover and the median income of the neighborhood.
Larger houses had more species. The size effect has been noted for many types of locations. Large houses simply have more places for insects to harbor. Higher income neighborhoods have larger houses, which may be the reason why numbers increase with income.
Three houses were home to over 100 species. These houses were all from neighborhoods with less than $100K median income but by no means the lowest income neighborhoods. These houses all had high levels of ground cover. People opt for grass lawns as a way to reduce the number of arthropod species living close to a house. Diverse and complex ground cover will harbor a larger number of species.
Only one house had fewer than 25 species of arthropod and it was rated as medium ground cover. Five of the six lowest numbers were found in houses that were surrounded by low levels of vegetation. For those who dislike indoor arthropods, this study suggests that despite your best efforts, you likely have more than 20 arthropods residing with you in your house.
*Misha Leong, Matthew A. Bertone, Keith M. Bayless, Robert R. Dunn, Michelle D. Trautwein. 2016. Exoskeletons and economics: indoor arthropod diversity increases in affluent neighborhoods. Biology Letters. Published 2 August 2016.