The terrestrial habitat has a number of properties that affect how parasites find hosts. Fluctuations in physical conditions can be extreme, and desiccation is always challenges the parasite's ability to survive while outside the host. There is relatively little Activedispersal of free-living parasite stages, except for those few parasites that can fly. Heat and chemical products from their hosts are used by parasites to find hosts, usually only at short distances. Light is an important cue for many parasites as they position themselves in locations where they are likely to encounter suitable hosts.
The biological properties of terrestrial habitats also affect host finding. Diversity of vertebrate and invertebrate hosts tends to be lower than in aquatic habitats. Many parasites that rely on passive means of host finding may still be still host specialists.