swarming around Los Angeles (but not migrating) during tin- 

 latter part of the summer and autumn of 1911. And in the fall 

 they were noted in great numbers in the canyons near Pasa- 

 dena. So it can be seen that the migration and abundance was 

 general over California, and the whole Pacific Coast during 

 1911, flying south-southeast or south. The recorded periods of 

 abundance are al)0ut ten years apart, which indicates its peri- 

 odic occurrence. Between these dates the butterfly is very- 

 rare ; only occasional specimens being taken in any locality. 



As to the reasons of this periodic occurrence it is probably 

 the coincidence of several factors which cause the abundance 

 of this species in certain years. Bryant found that the pupae 

 and perhaps also the larvae were parasitized to a large extent, 

 about 35%, which might greatly reduce the reproductive ca- 

 pacity of the butterfly. Bryant says "one factor governing 

 the phenomenon is the presence or absence of fortunate con- 

 ditions of hibernation." And adding the part played by 

 birds. And, of course, meteorological conditions, of which we 

 know so little, quite probably regulates the hatching of the 

 chrysalids over a great number of years ; this last seems to me 

 the most plausible factor, but at the same time the least under- 

 stood. The butterfly appears suddenly in great numbers, so it 

 would seem that the enemies play little part, and that favor- 

 able or unfavorable meteorological conditions .are the real 

 causes. 



In Europe V. polychloros is nearly related to our Califor- 

 nica; but I have no accessible records of any periodic occur- 

 rences or migrations, if there are any such. W. F. Kirby in 

 "The Butterflies and Moths of Europe," says: "It feeds on 

 elms and cherry-trees from I\Iay to August, and is sometimes 

 sufficiently abundant to be considered an injurious insect on 

 the continent." 



V. Californica was described by Boisduval (1) in 1852, he 

 says: "M. Lorquin n'en a pris ciu'un petit nombre d'indi- 

 vidus. ' ' Again in 1869 he says : ' ' Assez rare. ' ' M. Lorquin in 

 his l)rief sojourn evidently missed the years of the great 

 abundance. 



In several local lists of California butterflies published be- 

 tween 1902 and 1911, the writers mention Vanessa Californica 

 as rare; showing that although a few breed each year, the 

 bulk of the chrysalids await proper meteorological conditions 

 for emergence of the adult ; and that seems to be about every 

 ten years, more or less. We will look forward with interest 

 to the years 1919-1921, and be prepared to study this insect 

 again in detail, and compare with its previous record. If any 

 records have been overlooked, it is hoped they will be recorded, 

 so that our history of this insect may be as complete as possible. 



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