host by making flight more difficult, which may affect its aerial hunting ability or cause it to expend extra energy while carrying these passengers. Types Like all ecological interactions, commensalisms vary in strength and duration from intimate, long-lived symbioses to brief, weak interactions through intermediaries. Phoresy Phoresy is one animal attached to another exclusively for transport, mainly arthropods, examples of which are mites on insects (such as beetles, flies or bees), pseudoscorpions on mammals or beetles, and millipedes on birds. Phoresy can be either obligate or facultative (induced by environmental conditions). Inquilinism Inquilinism is the use of a second organism for permanent housing. Examples are epiphytic plants (such as many orchids) that grow on trees, or birds that live in holes in trees. Metabiosis Metabiosis is a more indirect dependency, in which one organism creates or prepares a suitable environment for a second. Examples include maggots, which develop on and infest corpses, and hermit crabs, which use gastropod shells to protect their bodies. Facilitation Facilitation or probiosis describes species interactions that benefit at least one of the participants and cause harm to neither. Necromeny Necromeny is one animal associating with another until the latter dies, then the former feeds on the corpse of the latter. Examples include some nematodes and some mites. See also Mutualism – where both organisms experience mutual benefit in the relationship Parasitism – where one organism benefits at the expense of another organism. Parabiosis – where both organisms occupy the same dwelling, but do not interfere with each other Symbiosis – long-term interactions between different biological species, which can be mutualistic, commensal or parasitic Synanthrope – species commensal with humans References External links Biological interactions Symbiosis