Microhabitat selection and movements of harvestmen (Opiliones: Phalangida) in gardens

Harvestmen are ubiquitous and abundant generalist predatory arthropods, yet little is known about their ecology and behavior.  They are known to consume a variety of pests, and due to their prominence in agroecosystems, great dispersal ability, gregarious tendencies, and their ability to remain active at low temperatures, they may have potential as agents of biological control in gardens. This study used mark and recapture methods to investigate the feasibility of sustaining a harvestmen population (Opiliones: Phalangida) in a garden. Unrestricted harvestmen movements were systematically followed, and small, wooden shelters shaped like lean-tos were placed as diurnal refugia for these humidity-sensitive predators in an attempt to prevent their emigration. Furthermore, it was predicted that more harvestmen would be observed in dense vegetation where microclimatic conditions (temperature & humidity) should be more favorable during the day.  Significantly lower daytime temperatures and reduced temperature variability were recorded in denser vegetation. More harvestmen inhabited dense vegetation than areas of sparse or no vegetation.  Significantly more harvestmen were observed in the proximity of shelters, thus, adding shelters reduced their tendency to leave the garden. The range and movements of harvestmen tended to be less in areas of dense vegetation and near shelters than in more exposed areas.