226 ENTOMOLOGICAL SOCIETY 



immigrants in Ohio," published in Science for February 3, 1893, 

 and subsequently in Bull. 51 of the Ohio Experiment Station, 

 has brought out some interesting facts regarding the probable 

 methods of introduction and lines of spread of certain species 

 through Ohio ; but he has failed to appreciate the fundamental 

 truths which govern the distribution of species in his region. 

 Among other things, he has failed to point out the important fact 

 that certain species to which the transition forms a barrier com 

 ing from the east can seldom reach Ohio by natural spread. The 

 carriage of infested plants or the steam transportation of individ- 

 duuls across the Alleghanian barrier is necessary for their intro 

 duction, and upper austral forms are quite as liable to reach Ohio 

 from the east by means of the great commercial paths to mid- 

 western New York and thence by natural spread through lower 

 Ontario and southern Michigan, or by the lake from Buffalo to 

 Cleveland, Sandusky, or Toledo, as by commercial jumps across 

 the mountainous regions of Pennsylvania. 



The whole subject is one which is fraught with the greatest 

 difficulty as well as interest. What I have just said is of the 

 most preliminary character and is advanced in this hurried way 

 only on account of its suggestiveness, and to induce consideration 

 and discussion of a comparatively new field. I have planned an 

 extensive investigation of the question, and am engaged in plot 

 ting on a large scale the actual distribution and injurious occur 

 rences of about 150 of our most destructive species, and in this 

 work hope to have the assistance of many of our entomologists. 



The paper was discussed by Messrs. Schwarz, Ashmead, 

 Merriam, and Gill. Mr. Schwarz spoke of the fact that there is 

 a large class of cosmopolitan species which defy all laws of geo 

 graphical distribution. Local influences may cause their absence 

 at certain points. He defined a cosmopolitan species as one that 

 occurs in both temperate and tropical zones of both hemispheres. 

 The scale-insects also seem to be not amenable to laws which 

 affect other species. In the case of introduced insects he had 

 noticed that, in general, forms introduced into the boreal regions 

 of this country are unable to spread into other zones. In the 

 same way species introduced into the southern States do not 

 spread in the more northern regions. This restriction seems 

 irrespective of spread in Europe. If species are introduced into 

 the middle States, however, they are more liable to spread both 



