The Arachnida represents one of the oldest and most recognized groups of predatory arthropods. The ecological success of scorpions and spiders as predators, in particular, is due in part to their production of venom that they use to subdue prey. In contrast, the harvestmen (Order Opiliones) are omnivorous, acting as predators or scavengers, but also feeding upon fungi and plant tissues, such as fruit. These groups of arachnids are very abundant in tropical environments, so behavioral interactions among them are inevitable. In this paper, we describe two cases of interactions between scorpions, spiders and harvestman, observed during field work in rural areas in Panama.