of Danais Archippus. 103 



the attacks of the same, would be most necessary to a 

 few lepidopteral colonists, struggling in a new land to 

 establish their naturalization. 



3rdly. Insects which quickly develop from egg to imago 

 can effect their transformations during the xoarmth of a 

 short summer in a higher latitude than their original 

 habitat. — I have not hitherto met with notice of this im- 

 portant factor. Taking an example from the vegetable 

 Avorld, the annuals which adorn our gardens, though often 

 indigenous to more tropical climes, are yet enabled to run 

 their course from the seed stage to leafing and flowering 

 and back to the seed stage again during our short sum- 

 mer, solely through the rapidity with which they perform 

 their cycle of existence. Like causes must produce like 

 results in the life of a butterfly, that can effect its trans- 

 formation in regions so climatically diverse as Canada and 

 Central America. The lai-va of D. Archippus has but 

 three moults, and frequently acquires its fidl growth within 

 three weeks from hatching, and remains in the pupa con- 

 dition only about ten days;* whilst, according to Mr. 

 Edwards, there are, at least presumably, three broods yearly 

 in W. Virginia — one early in June, the second about the 

 beginning of August, and in September or October is a 

 third bi'ood, which hybernate.f 



To recapitulate. — Starting with the assumption of 

 North America as the original home of this butterfly, 

 Ave have seen that winds and currents are in all cases 

 in strict accordance with its distribution, whether from 

 one side of the continent to Europe and the Azores or 

 from the other to the South Sea Islands and Australia; 

 that its high flight and gregarious habits would favour 

 its dissemination by gales of wind ; that prevalent winds 

 woidd continue to waft it in the direction of its new abode ; 

 and that beneath it would flow oceanic currents, bearing 

 their natural flotsam and jetsam, fi-equently trunks of trees, 

 in the same direction. Analogy would lead us to suppose 

 that the occurrence of these butterflies being blown out to 

 sea would be a frequent one ; but the number that could 

 successfully cross a wide ocean would be very few and 

 oidy at very wide intervals of time. Now we learn from 

 JNIr. Kilcy that these butterflies hybernate through the 

 winter and often appear in immense swarms in the autumn. 



• Kilcy. Ih. 



f CiiiKuliiin Kntonioloi^ist. 



