22 THE CANADIAN ENTOMOLOGIST. 



partial breeders in our territory. How far north the permanent residence 

 of the Cotton Moth obtains is not yet known. I am the first to point out 

 that it is winter-killed over much of the territory which its summer migra- 

 tions cover as a moth. I have seen how the migration takes place. The 

 moths crawled out in numbers on my plantation during one or two days, 

 and I anticipated a third and more destructive brood of caterpillars. 

 The next morning not one perfect moth was to be seen. On the ground 

 crawled a few cripples with unexpanded wings, to be killed by the sun 

 and the ants. There was no third brood ; the moths had migrated, 

 been swept by the winds to the north during the night. I have alluded 

 to the influence of the winds upon the time of arrival of the Cotton Moth 

 on the Atlantic coast. 



The "original" part of my work on the Cotton Worm was my dis- 

 covery that it hibernated in the moth state ; that it was winter-killed over 

 a part of the territory it occupied both as larva and moth during the 

 summer; that in the south it had no other food plant than cotton. I 

 accounted for the moths in Canada in the fall by considering them wind- 

 migrants. No alternative food plant is known in the north. In the 

 south, as I originally stated, the worms migrate from eaten-out cotton 

 fields, leaving the weeds and vines untouched, in search of fresh cotton. 

 I identified the insect with the South American Aletia argillacea of 

 Hiibner, and stated my theory which I arrived at from a study of the 

 habits of the moth and from a knowledge of the cotton plant itself, which 

 like its parasite is not indigenous with us. Both have changed their 

 normal condition. Man brought the cotton plant, which under culture 

 and in our climate has become an annual, itself winter-killed in part, but 

 so more productive of cotton ; the winds brought the moth and the 

 cultivated cotton fields supplied abundant food. I pointed out the 

 yearly seasonal spread of the moth from south to north. 



But to leave the special subject of the Cotton Worm, which is inter- 

 esting by itself as illustrating one of the sources of the southern element 

 in our Lepidopterous fauna, and to proceed with our analysis. The third 

 element in our fauna is that which is North American per se, that is, 

 which is descended from a pre-Glacial North American fauna, or which 

 has become so modified from its original source as to be classed as North 

 American. Here is a very difficult study in a consideration of the 

 characters of our Lepidoptera. I have taken Cressojiia juglandis as a 



