Microlepidoptera 



of the 

 Philippine Islands 



Introduction 



Between the continents of Asia and Australia lies a region well 

 known to every biologist since the classical collecting expedition of 

 Alfred Russel Wallace in the 1860s. It has become famous for its 

 rich and variegated fauna, its complicated geological history, and the 

 interesting aspects of its zoogeography. 



This region consists roughly of three parts. One is a partly sub- 

 merged promontory of Asia, the so-called Sunda shelf upon which 

 the Greater Sunda Islands are situated. The second part, a similar 

 bridgehead of the Australian continent, the also partly submerged 

 Sahul shelf, bears New Guinea and dependencies. The third part 

 forms the so-caUed Wallacea and is situated between the other two. 



The well-known theory of Penck (1894) suggests that during the 

 glacial periods of the Pleistocene so much water was extracted from 

 the oceans, due to the forming of an icecap over the Northern Hemi- 

 sphere, that the seas were about 100 fathoms more shallow than they 

 are today. At that time, the above-mentioned and now submerged 

 plateaus must have formed the land bridges so important for the 

 animal distribution. 



Wallacea does not rest upon a submarine plateau and consists of 

 separate islands or island groups that may have retained their archi- 

 pelagic character for a very long time. The northern part of this 

 region is comprised of the Philippine Islands, with which we are here 

 concerned; the southern, of Celebes and certain Lesser Sunda Islands. 



The zoogeographic history of the fauna of the region seems to be 

 thus: in early Tertiary (the Oligocene or Eocene) the northern island, 

 Luzon, was connected through Formosa with the Asiatic continent. 

 Evidence of this connection is suggested by some relicts in the moun- 

 tains of Luzon, (e.g., Pinus with the Cross Bill and certain continental 

 Asiatic butterflies such as Pieris, Pyrameis, and Argynnis). 



Other land bridges, which developed later in the Pliocene and 

 Pleistocene, have left more distinct traces. A broad connection 



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