1961] 
Taylor and Wilson — Ants 
141 
species than it does — and considerably more than Lord Howe. The 
reason for the apparently sub-normal size of the Norfolk Island 
fauna may be sought in the correlation between faunal size on the 
two islands and the following two factors: 
1. Ecological Diversity: The published reports of the terrain and 
the state of the vegetation on these islands suggest that Lord Howe 
is ecologically much more diverse than is Norfolk Island. In- spite 
of its much smaller size it may, therefore, be capable of supporting 
a larger and more varied ant fauna. Conversely, Norfolk Island may 
have a lower carrying capacity due to its lower ecological diversity, 
so that its fauna, although proportionately smaller than that of Lord 
Howe, is nevertheless saturated. 
2. Distance from Australia: The apparent correlation between 
faunal sizes on these islands and their distances from Australia 
contrasts with Wilson’s (1961) finding in Melanesia, where such 
correlation is lacking. This situation may be due to the absence of 
intermediate islands between those under discussion and Australia — 
islands which might provide assistance as “stepping stones” to colonists. 
According to this hypothesis the small size of the Norfolk ant fauna 
is due to the fact that too few species have reached the Island to 
saturate its carrying capacity. 
If mere distance from Australia does have the filtering effect 
envisaged it may be assumed that there is a maximum range of 
natural overseas dispersal of the Australian fauna. As far as the 
ants are concerned, Raoul, in lacking indigenous Australian elements, 
may be considered to be outside this range. 
It is not possible, at present, to evaluate the relative importance 
of these two factors in determining the size of the Norfolk Island 
ant fauna, but the problem would certainly be worthy of attention 
by future field workers in these areas. 
Lord Howe Island also has significantly more endemic ant species 
than has Norfolk; each of these represents a stock which has diverged 
from its Australian progenitor and in no case has splitting or radiation 
taken place in situ on the island. The ecological diversity of the 
island, coupled with the competitive pressures which must arise in 
such a dense fauna, has probably caused this specialization of stocks, 
with consequent phyletic change to the point of formation of an 
endemic species in some lineages. 
Clipperton Island 
Clipperton Island is a lonely coral atoll about four miles in 
diameter, lying at N. lat., 10.18 and W. long., 109.15. It is 1,800 
