On the basis of the criterion that a successful introduction is likely to be a non-nest-dwelling generalist species with relatively wide environmental tolerance or a more specialized species with avian or domestic animals as hosts, a list of the most likely candidates for invading ixodid tick species can be constructed (Table 7.2). In most cases, such introductions will become more likely with warmer, drier climates such as those in southern European and North Africa, although species which currently live where there are continental climatic conditions may also benefit. Eleven species (57.9%) occupy arid, semiarid, or steppe environments, whereas Haemaphysalis inermis, Haemaphysalis parva, Hyalomma lusitanicum, Hyalomma marginatum, Ixodes gibbosus, Ixodes redikorzevi, Rhipicephalus turanicus, and Rhipicephalus (Boophilus) annulatus are all found in less harsh Mediterranean climates. With the exception of I. redikorzevi, which has been most commonly reported from rodents and other small mammals, and R. (B.) annulatus, which is predominantly a cattle tick, all of these species have a wide host range which frequently includes stock and companion animals (Table 7.2). Of particular importance are those species associated with such hosts as well as those which infest birds, particularly migratory species, as these hosts provide a likely method of cross-border movement.