FIFTEENTH ANNUAL MEETING. 53 



ornament. The Australian acacias have long been popular in 

 California, and manv of these beautiful trees may be seen grow- 

 ing there in the towns and country places. In the same State, 

 less than a dozen years ago, the inspection of a bushel or two of 

 apples or pears would perhaps have resulted in finding one or 

 two specimens of the larvae of the codling moth {Trypeia pomon- 

 ella, Walsh). Since that time the fruit growers have had to fight 

 it as a pest, and have been put to great expense to cleanse their 

 orchards of this and other injurious insects, the stock of which 

 was incidentally introduced, as is generally believed, on trees 

 from the East. In the climate of the west coast, which is par* 

 ticularly favorable to the development of this class of animal 

 life, the increase of pestiferous insects has been surprisingly 

 rapid. 



The trade in plant seeds is enormous and extends throughout 

 the entire world. The increase and spread of noxious plants is 

 largely owing to their seeds being mixed with the seeds of de- 

 sirable plants, and the weeds of one region thus become the 

 weeds of another, remote from the original habitat. The May 

 weed of the New Englander, Anthemis cotula, or European dog- 

 fennel, has through the operations of nature and the incidental 

 assistance of man, put a girdle around the earth. The Chrys- 

 anthemum vul^are is a pretty, but to the farmer an obnoxious cos- 

 mopolite, popularly known as white-weed and ox-eye daisy.. 

 Another plant pest, Cnicus arvensis, familiarly called Canada 

 thistle, though of European origin, has spread it might be said 

 to the uttermost bounds of the earth. So far as America is con- 

 cerned, it, the latter country, has reciprocated by contributing 

 the horse weed, Erigeron canadensis, to the pestiferous plant stock 

 of Europe. 



From mammalian, insect and vegetable forms, let us now 

 briefly glance at molluscan species. The slowness of the snail's 

 pace is proverbial. Yet we find that several species are widely 

 dispersed, not by reason of their own means of locomotion, but 

 as an incident of commercial intercourse. A species of slug. 

 Limax heivsiowni^ Cp., has become quite common of late years in 

 the grass plots and lawns of San Francisco and vicinity. There 

 is good reason for regarding it as an incidental importation. 



