372. CALIFORNIA ACADEMY OF SCIENCES. 



ous plants (called milkweed), which type does not grow 

 on this side of the bay. In the following year I found a 

 great number of the larva on A sclepias fascictilaris grow- 

 ing on marshy grounds near Brooklyn, then called San 

 Antonio. Some years afterwards I found the cater- 

 pillar in a garden in San Francisco on an exotic plant of 

 the Asclepias family, Gomphocarj)us Curassaviais. 



From that time the butterfly has visited our streets every 

 fall, and swarms of this insect working against the west- 

 ern current of air, peculiar to our summer months, fly 

 out to the lighthouse, where they disappear, probably 

 drowned in the ocean. 



Since the year 1880 they have not visited the city, which 

 omission easily could be accounted for by the circum- 

 stance that the marsh where their food plant, the Ascle- 

 pias . formerly grew, was converted into fields and or- 

 chards. 



In this instance the insect has but little power of adap- 

 tation to new food, because it has shown itself dependent 

 upon plants of the milkweed family and became locally 

 extinct, at least temporarily in a district where the ground 

 containing the milkweed was ploughed over. But, on 

 the other hand, it has shown wonderful powers of adap- 

 tation to different climates; proof of it, its wide geograph- 

 ical range and the colonies formed in countries beyond 

 the sea, where it probably has been carried in its chrysalis 

 state in the ballast of vessels. 



2. Pyrameis Cardni, the most cosmopolitan butterfly 

 in existence, of an almost unlimited power of adaptation, 

 because with the sole exception of the real tropics, Aus- 

 tralia and the regions beyond the Arctic circle, it exists 

 everywhere. Even the Australian species, Pyrameis 

 Kershawii, by some authorities is considered identical 

 and not merely related. 



