In encounters with predators, sclerosomatid harvestmen may employ a variety of defensive tactics including the voluntary detachment of legs (autotomy). The long-term costs of this evasive defense are not fully understood, but prior studies have documented negative consequences for terrestrial locomotion and foraging. In this study, we investigated the impact of leg loss upon locomotion in adult harvestmen (Leiobunum spp.). In southeastern Virginia, these harvestmen regularly climb vegetation and occupy perches on tree trunks, branches, and leaves that are often 1–2 m or more above the ground. In our study, we measured walking and climbing speeds for individuals with 5, 6, 7, and 8 legs. The results of our field surveys conducted over three seasons revealed relatively high frequencies (36–63%) of leg loss. We also found that individuals with six legs occupied perches that were significantly lower in the understory than those with eight legs. In the lab, we observed significantly slower walking speeds for individuals missing one or more legs. We also found that individuals with five legs climb significantly slower than individuals with eight legs. On the bases of the observed frequencies of leg loss in the field, we infer that leg autotomy is a common (and effective) evasive tactic used by harvestmen. However, the reduction in walking and climbing speeds resulting from leg loss may also affect habitat selection, (e.g., perch height) and may ultimately reduce the survivorship of individuals in future encounters with predators.