FAUNA OF THE MONTE BELLO ISLANDS. 651 
pointed out the absence from the collections of several species so 
widely spread as to be generally found in any locality in Australia. 
He suggests, therefore, that the islands have once been largely 
denuded of the original spider fauna, and were repopulated 
subsequently with other species. These seem mostly to have come 
from the south-west by the trade-wind course, for the majority 
could certainly have been wind-borne. ‘These remarks in some 
measure seem to apply to other groups of animals, though many 
species are northern, occurring in Queensland and the Northern 
Territory, probably having come down by the hurricane course. 
That an almost complete depopulation of the islands could have 
occurred is by no means an improbability, when their small size 
and the prevailing meteorological conditions are considered. It 
will be noted that the vast majority of the specimens recorded are 
from Hermite. ‘This island was certainly the most thoroughly 
worked, though the others were frequently visited, but its fauna 
was at least three times as large as that of any of the smaller 
islands. This is merely a demonstration of the obvious fact that 
the smaller the island, the less will be the chance of a sufficient 
number of individuals surviving to perpetuate the species after a 
particularly severe and prolonged period of drought. It is indeed 
remarkable that the Wallaby has been able to survive, considering 
that it lives entirely in the open, and has nowhere to shelter 
except amongst the Spinifex during the hurricanes, when trees 
and bushes are torn up by their roots, and sand and shells blown 
about with such violence as to cut deeply into wood. 
In considering this point, it 1s well to remember that little work 
has been done in the North-West of Australia, and the distribution 
of some species may be found to be much more extended than is 
at present supposed. Moreover, other forms, which might be 
looked upon as island species, may really be quite common on the 
mainland, though as yet unrecorded. However, the well-known 
generalisations with regard to island faunas ( using the word 
‘island’ in the zoological sense) hold good:—the wingless forms 
not easily transported comprise most of the undescribed forms, 
being In many instances clearly the modified representatives of 
mainland species, whereas the easily transported winged species 
are for the most part of wide distribution. There are many 
anomalies, which can only be explained by considering individually 
the habits of each species and the prevailing meteorological 
conditions. Amongst the Longicorn beetles, for example, there 
are two abundant species, of which one, Mictotragus arachne, has 
the elytra completely fused, and is absolutely identical with the 
form occurring abundantly upon the mainland opposite. The 
other, Symphyletes, sp.n.(?), a form with well-developed wings, is 
confined to Hermite. A possible factor in such local distributions 
is perhaps to be looked for in the whirlwinds which area character- 
istic weather-feature of the district. These disturbances can be 
observed almost any day, and must certainly be regarded as an 
important distributing factor. Of the two beetles in question, the 
Proc, Zoou, Soc.—1914, No, XLY, 49 
