264 CALIFORNIA ACADEMY OF SCIENCES [Proc. 4TH SER. 
Schistocerca and two of Sphingonotus, each of which is 
represented by a recognizable subspecies or variety on each 
of several islands. The resemblance to the two species of 
Camponotus is further shown by the fact that Schistocerca 
melanocera is represented by two subspecies on Albemarle 
and that two forms of Sphingonotus tetranesiotis occur on 
Barrington and two on Indefatigable. 
On the whole, the ant-fauna of the Galapagos is decidedly 
poor for islands lying on the equator and possessed of an 
abundant and varied flora. Dr. Williams informs me that 
even the colonies of the species which do occur on the larger 
islands are far from numerous and are found only after 
diligent search. Only one or two forms have been taken 
on most of the islands. Chatham has six, Charles and Albe- 
marle each seven, and Indefatigable eight, but even these 
numbers indicate a very limited fauna. At first sight this 
might be regarded as evidence that the ant-fauna was acci- 
dentally introduced and had lingered on, undergoing slow 
varietal and subspecific modification in response to the differ- 
ent physical conditions on the various islands. In my opinion, 
however, no such conclusion can be legitimately advanced. 
The poverty of the fauna is more probably due to adverse 
conditions, as ants are not fond of volcanic soil, probably 
because it gives off deleterious gases in the process of decom- 
position, or does not afford proper nesting sites, as would be 
the case with the great stretches of hard lava said to occur 
on some of the Galapagos islands. he climatic conditions, 
moreover, are decidedly unfavorable, as the littoral zone of 
the islands up to 800 feet is very arid, while the more densely 
wooded portions, at higher levels, are cool and damp. I 
have pointed out in other publications that moisture coupled 
with a low temperature is very unfavorable to ant-life and 
have called attention to the meagre faunas of such regions 
as New Zealand, Great Britain and the Selkirk Mountains 
of British America in support of this contention. 
The bearing of my study of the Galapagos ants on the 
two great rival hypotheses that have been advanced to ac- 
count for the origin of the islands and of their biota, is 
indecisive. A study of the literature shows that the problem 
is still far from solution and that probably as much evidence 
