ABSTRACT
Although most of us, whether lay person or scientist, do have an idea of what is meant by 'migration', it is difficult to find a generally accepted definition of the term. This is largely because those who work on different animal groups tend to use the word in rather different contexts. For instance, ornithologists usually regard migration as some form of regular, long-range movement between wintering and breeding areas, and expect an element of predictable seasonal 'to and fro-ness' of both individuals and populations. In contrast, an entomologist would have little expectation
that populations, let alone individuals, of migratory aphids or locusts will return to the place from which they departed.
