162 Distribution of Moths of the Sub-family Bistonina ?. 



more certain by the occurrence of its most primitive double- 

 spurred species Zamacra excavata side by side with the one- 

 spurred form, Z. juglansiaria in Japan. 



Very probably, the genus arose at some point northward 

 of its present area and, with other forms of late Miocene and 

 early Pliocene origin, was forced southward along the coast 

 and into the warmer coastal plain which then embraced not 

 only the present coast, but also the basin of the Yellow Sea 

 and Japan by of the approach of the Ice Age. 



The discovery of the species with two pairs of posterior 

 tibial spurs alongside those with only one pair shows that, even 

 in these early days, the tendency of the Non-Boarmioid 

 BistonincB to lose one pair had already manifested itself and, 

 consequently, the final separation of Japan from the mainland 

 shut off species of both sub-genera. 



However, Acanthocampa occurs in North Persia, whence 

 we see that both sub-genera had early begun to send offshoots 

 along the route adopted by the earliest horde of Eastern 

 Asiatic migrants pressing into Europe. These, in all proba- 

 bility, skirted the southern shores of the great Central Sea of 

 early Pliocene Asia, passing between it and the long uplifted 

 Altai and neighbouring mountains. When Acanthocampa had 

 reached Persia, its momentum seems to have been spent, for 

 the sub-genus is lacking further to the west ; it is not so, 

 however, with Zamacra, for it reappears just west of Acan- 

 thocampa in Mesopotamia in the very familiar form of Zamacra 

 flabellaria. On reaching the Tigris, it had swept onward into 

 Syria and Asia Minor. No northward course was open for 

 the Asian Sea barred the way. Evidently, when it arrived 

 in Syria, the early Pliocene disturbances which tore that land 

 asunder had already set in for Z. flabellaria failed to pass into 

 Egypt. Instead, it marched forth from Asia Minor into 

 Greece which then, with Asia Minor, Cyprus and Crete, formed 

 one continuous land mass. 



From this area, if one judges from its distribution now, it 

 has pursued a most erratic and, in the light of present day 

 geography, an impossible course. It seems to have passed 

 on from Greece to Sicily without entering Italy — an extraor- 

 dinary occurrence. But why, we ask, does this strange failure 

 in Italy exist ? The answer is plain. When Z. flabellaria 

 was moving, Italy, as we know it, was yet a land of the future. 

 All that was developed in early Pliocene times was a rocky 

 peninsula jutting out from the Alps into the Early Pliocene 

 North-western Mediterranean Sea. In its place, there was 

 a huge tract of land stretching westward from Greece and 

 embracing Crete, Sicily, Malta, Sardinia, Tunis and Morocco. 

 That such a mass then existed can be proved, independently 

 of any consideration of the western Mediterranean Flora and 



Naturalist, 



