314 Distribution of Moths of the Sub-family Bistonince. 



Thus once again, confirmatory evidence is gained that 

 Phigalia is a genus originating in Asia for, necessarily, we have 

 to fix its home somewhere in Siberia to allow for its contact 

 with its immediate relatives Microbiston and Chondrosoma. 

 Somewhere then in the old basins of the Obi and Yenesei, 

 Phigalia took its rise, and thence worked its way east and west 

 in northern latitudes, very early in its wanderings throwing 

 off Microbiston or what, in those far off days, represented it. 



Almost equally early a form not far removed from Phigalia 

 pedaria came into being and lagged behind ; but the prototype 

 pressed on in its westward march reaching the American area 

 before the inevitable southward flight of animals and plants 

 began. When that event did occur, following the same route 

 as Amphidasys cognataria and crowds of other insects in like 

 plight, it took sanctuary in that refuge for trees and arboreal 

 forms, the Atlantic and Gulf States of America. 



But the reign of the Ice King was not to last for ever ; 

 century after century elapsed, but, in the end, genial conditions 

 did for P. titea what they did for its companions. As in 

 byegone ages, its northern home was in part reopened. Slowly 

 the forests of deciduous trees readvanced and with them 

 went the insect, regaining lost ground as far north as Canada 

 just as did A. cognataria and L. ursaria. Unlike these, it has 

 managed to retain some hold on its home of refuge for it 

 yet inhabits Texas. No doubt this possibility is caused by 

 its appearance early in the year and by its rapid feeding up, 

 coupled with its powers of activating as a pupa. 



Its history thus, in all essentials, is parallel with that of 

 other early forms we have already discussed. 



Next we must return to the form which we shall now know 

 as P. pedaria. To the west and to the east it passed ; not, 

 we must be careful to note, over Transcaspia and to the north 

 and south of the Caspian Sea. Had the insect occurred so 

 far south no passage was open in that direction; the Aralo- 

 Caspian Sea still maintained its maximum area. On the 

 contrary, its westward course (and its eastward one too) was 

 to the north of the Eurasia of to-day. Therefore, when, in 

 Northern Europe of late Pliocene times, subsidences occurred, 

 followed by the fall in temperature indicating that the Glacial 

 Period was at hand, P. pedaria fell back to the south, delaying 

 its retreat by assuming a birch diet. Its final withdrawal had 

 to come, and it accompanied the great host of later fugitives 

 into Southern Europe until the Glacial night-mare was past. 

 With the vanishing of the ice, it very early made a move, 

 relying on its powers of adapting itself to new foods, and 

 managed to reach and colonise the whole of Britain ere our 

 islands were disjoined from the mother continent. 



But P. pedaria for its continuity had not to rely solely on 



Naturalist, 



