We investigated abundance and web characteristics (web elevation and spiral area) of the spiny orb weavers Micrathena gracilis (Walckenaer 1805) and Micrathena mitrata (Hentz 1850) using transect surveys in oak-hickory forest stands in west-central Illinois. Surveys resulted in 153 collected individuals or observations of adult females (70 M. gracilis and 83 M. mitrata). Peak abundance of both species occurred in late July, with a density of 0.03 females per m² for each species. Web spiral area and web elevation were both greater for M. gracilis than M. mitrata. Micrathena mitrata web spiral area was larger in plots in which spiders had been previously removed than in plots without removal. These results suggest that the two species have different vegetation structure or microclimate preferences, and may respond to availability of unoccupied habitat differently.