May 19, 1921 hopkins: problems in bioclimatics 223 



BIOCLIMATICS. — Intercontinental problems in bioclimatics; with 

 special reference to natural and artificial distribution of plants and 

 animals} Andrew D. Hopkins, Bureau of Entomology. 



One of the most important subjects for the consideration of ento- 

 mologists, botanists, general biologists and agriculturists in the past, 

 and for the future, relates to the introduction of plants and animals 

 from one part of the world to another. This subject is largely one of 

 the relations between life and climate, with regard to the original 

 home of a species, the environments under which it has developed, 

 the range and limits of its natural distribution on one continent, the 

 place of its artificial introduction to another, its establishment there, 

 and its natural or artificial spread from the point of entry. 



This address is concerned with some of the principles of the bio- 

 climatic law, methods of application and results as revealed by a 

 study, just completed, of the relations between the advance of spring 

 in eastern North America and western Europe as based on certain 

 phenological events that characterize a particular phase of such ad- 

 vance. This study was made in connection with, and as a prelim- 

 inary to, a more comprehensive investigation of the relation of the 

 law to the bioclimatic zones of the continents, as a key to solving 

 some of the problems in artificial distribution of desirable plants and 

 animals, in the belief that the true guide to success is to be found 

 in zones of similar bioclimatic types. 



While the subject of the bioclimatic law and its application to re- 

 search and practice has been discussed in papers before this Society, 

 and in recent publications, it is apparent that some of the principles 

 on which the law is founded, and some of the features in the system 

 of application, are not generally understood. Consequently there 

 are skeptics as to the sound basis and the scientific and practical 

 value that we claim for it, which is an excuse for repeating our inter- 

 pretations. 



The bioclimatic law is a law of life and climate as related to the 

 geographical coordinates latitude, longitude and altitude. It includes, 

 as one of its principles, an average, or constant, rate of variation with 

 variations in geographical positions, as manifested by the advance of 

 the seasons and coincident phenomena, and. by the geographical dis- 

 tribution of living organisms and types of climate. 



'Address of the retiring president of the Biological Society of Washington, presented at 

 a joint meeting of the Academy and the Biological Society on April 2, 1921. (Received 

 April 12, 1921.) 



