transmission would be in most cases quite
involuntary, and not dependent on their own powers of flight as with birds;
and thus the chances against the same species being frequently carried to
the same island would be considerable. If we add to this the dependence of
so {255} many insects on local conditions of climate and vegetation, and
their liability to be destroyed by insectivorous birds, we shall see that,
although there may be a greater probability of insects as a whole reaching
the islands, the chance against any particular species arriving there, or
against the same species arriving frequently, is much greater than in the
case of birds. The result is, that (as compared with Britain for example)
the birds are, proportionately, much more numerous than the beetles, while
the peculiar species of beetles are much more numerous than among birds,
both facts being quite in accordance with what we know of the habits of the
two groups. We may also remark, that the small size and obscure characters
of many of the beetles renders it probable that species now supposed to be
peculiar, really inhabit some parts of Europe or North Africa.

It is interesting to note that the two families which are pre-eminently
wood, root, or seed eaters, are those which present the greatest amount of
speciality. The two Elateridae alone exhibit remote affinities, the one
with a Brazilian the other with a Madagascar group; while the only peculiar
genera belong to the Rhyncophora, but are allied to European forms. These
last almost certainly form a portion of the more ancient fauna of the
islands which migrated to them in pre-glacial times, while the Brazilian
elater appears to be the solitary example of a living insect brought by the
Gulf Stream to these remote shores. The elater, having its nearest living
ally in Madagascar (_Elastrus dolosus_), cannot be held to indicate any
independent communication between these distant islands; but is more
probably a relic of a once more widespread type which has only been able to
maintain itself in these localities. Mr. Crotch states that there are some
_species_ of beetles common to Madagascar and the Canary Islands, while
there are several _genera_, common to Madagascar and South America, and
some to Madagascar and Australia. The clue to these apparent anomalies is
found in other genera being common to Madagascar, Africa, and South
America, while others are Asiatic or Australian. Madagascar, in fact, has