The wandering spiders Ctenus amphora Mello-Leitão 1930 and Ctenus crulsi Mello-Leitão 1930 are sympatric in central Amazonian rainforests; however, the former is more abundant in sandy soils and the latter in clay soils. In previous studies authors suggested that C. crulsi is competitively superior on clay soils and avoids sandy soils. Thus, we hypothesized that these species differ in their responses to the soil type. To test this, we placed 37 C. amphora and 30 C. crulsi in chambers providing two choices (sand or clay) and compared the proportion of observations in each to evaluate both species' preferences. Ctenus crulsi significantly preferred clay to sand (P < 0.01), while C. amphora showed no evidence of preference between two types of soil. We discuss the possible ecological consequences of this difference in behavior. This is the first study that experimentally shows a difference between the responses of spider species to soil type as an explanation of their coexistence.