290 CALIFORNIA ACADEMY OF SCIENCES [Proc. 4th Ser. 



Introduction 



The author regrets that he is unable to include in this paper 

 all the species of Lepidoptera collected on the islands, for while 

 this order is scantily represented in the region under considera- 

 tion, the smaller and less conspicuous forms present difficulties 

 which would cause considerable delay; and rather than to 

 permit this, he has deemed it advisable to publish at present the 

 butterflies and Sphinges with such observations on other Gala- 

 pagos Lepidoptera as may assist in showing the facies of this 

 fauna and in rendering an explanation of its origin and devel- 

 opment. 



A single fauna need not be treated in its entirety to show 

 its relationships with others, though where possible, the whole 

 fauna should be studied. 



The Galapagos Archipelago (belonging to Ecuador) is sit- 

 uated on the equator, about 600 miles from the west coast of 

 South America, and a little more than 700 miles from Veragua, 

 with Cocos and Malpelo Islands intervening. This group is 

 therefore considerably closer to the mainland than are some 

 other oceanic islands, as the Hawaiian Islands, 2350 m. ; St. 

 Helena, 1100 m. ; the Azores, about 900 m. ; and the Bermudas, 

 about 700^ m. I have considered the Galapagos as oceanic as 

 regards their natural history; whether they issued in the first 

 place from the bed of the ocean, or whether they were of con- 

 tinental origin, provided they were once completely submerged,^ 

 or all living organisms thereon otherwise totally destroyed 

 simultaneously by volcanic activity, as the flora and fauna 

 would still be of oceanic character, i. e., transported across 

 water to the islands, a condition that the writer believes has 

 happened. To quote Wallace in his "Island Life," the Gala- 

 pagos Archipelago "occupies a space of about 300 by 200 miles. 

 It consists of five large and twelve small islands; the largest 

 (Albemarle Island) being about eighty miles long and of very 



1 These figures are taken from Wallace's "Island Life." According to F. M. Jones 

 (Ent. News XXI, 16S, 1910), the Bermudas are 575 nautical miles from Cape Hat- 

 teras, North Carolina. 



- There is good evidence that the Galapagos Archipelago was once one large island 

 which by subsidence has formed the many smaller islands. This view makes it easier 

 for us to explain the existence on all or most of the islands of closely allied species 

 or varieties. 



