Activity Patterns of Two Species of Neotropical Harvestmen (Arachnida: Opiliones) from Costa Rica

Abstract

Natural history studies serve as important foundations for future investigations of behavioral ecology and provide biologists with critical information needed for the development of empirical research programs. Relatively little is known about the biology of most species of Neotropical harvestmen in Central America. In this field study, we investigated the activity patterns of two common species Cynorta marginalis (Cosmetidae) and Prionostemma sp. (Sclerosomatidae) in a wet tropical forest in Costa Rica. We used visual encounter surveys along randomly selected transects to compare the relative abundance of these species during morning, afternoon, evening, and late night sampling periods. To generate ethograms, we observed up to three individuals of each species for 10 min along each transect, generating 69 behavioral observations for C. marginalis and 51 for Prionostemma. Both species occupy perches on vegetation and are generally nocturnal with respect to activity. After dusk, individuals of C. marginalis actively climb, interact with conspecifics, and forage on the surfaces of small and large trees. During the day, adult Prionostemma form relatively inactive clusters of up to 40 individuals on arboreal perches and descend to the leaf litter after dusk to forage.

Diversity and Habitat Use of Neotropical Harvestmen (Arachnida: Opiliones) in a Costa Rican Rainforest

“…1 and 2 make vertical migrations during the day [18], similar to behaviors described by Todd [6] for the sclerosomatid L. rotundum. Our data also support this pattern.…”

“…Individuals may undertake daily vertical migrations, descending to the leaf litter at dusk to forage [8,17,18]. Abiotic factors, especially temperature and humidity, significantly influence the distribution, habitat selection, and activity patterns of harvestmen [4,6,8,19] as well as community structure along elevational gradients [11,[20][21][22].…”

“…Several species inhabit leaf cutter ant nests [51], while others occupy bromeliads [52] or rely on bromeliads for reproduction [53]. Individuals of some temperate sclerosomatid species are known to make vertical migrations-climbing on trees during the day and descending at dusk to forage on or near the ground [6,17,18]. In montane rainforests of Trinidad, two syntopic species belonging to the family Cranaidae often use fallen palm frond sheaths as diurnal shelter [22] or oviposition sites [45,54,55].…”

Communal roosting sites are potential ecological traps: experimental evidence in a Neotropical harvestman

“…Hedin et al 2008;Horváth et al 2009;Horváth et al 2007;Kriska et al 2006;Ries and Fagan 2003) and can serve as valuable indicators of disturbance (Uehara-Prado et al 2009). Harvestmen are among the most abundant arthropods in tropical forests (Wade et al 2011) and are strongly affected by habitat fragmentation and other anthropogenic disturbances (Bragagnolo et al 2007). Our results highlight a new mechanism-chemically mediated conspecific attraction-that may cause degraded habitat to become an ecological trap.…”

“…We studied a population of Prionostemma (not described below the genus level) in which individuals forage solitarily at night and roost in aggregations during the day , as seen in other species in this genus (Coddington et al 1990;Wade et al 2011). Roosting aggregations usually form on the trunks or fronds of spiny palm trees (Bactris, Astrocaryum) in the forest understory.…”