2i6 POPULAR SCIENCE MONTHLY 



long before they could have reached the full size of which the species 

 is capable. My present information indicates that there are yet some 

 districts in the western part of the United States, notably portions of 

 California, in which the black locust tree, which was originally grown 

 there from eastern seed, has not yet been injured by the borers. But 

 the borers are surely lurking in all other parts of our country in which 

 that tree has grown for any considerable number of years. Further- 

 more, judging from the facts already stated and the remarkable case 

 of destruction of that tree by the borers which occurred in the great 

 valley of the Upper Mississippi between forty and fifty years ago, one 

 may reasonably fear that those farther western groves will yet suffer 

 like disaster. 1 



The case referred to is peculiar, and fraught with important sug- 

 gestions to those who are now contemplating the* artificial propagation 

 of the black locust tree. In the early half of the past century there 

 occurred a strong migratory movement of families overland from 

 eastern states to Illinois and Iowa, who carried with them in their 

 wagons the seeds of various kinds of trees, among which were those of 

 the black locust. Those seeds were planted in the fertile soil of the 

 new homesteads, where they germinated promptly and the seedlings 

 grew vigorously and healthfully. The settlers thus ' stole a march ' of 

 many hundred miles on the borers, for neither they nor the tree upon 

 which they exist had then occupied a large part of the country which 

 the emigrants traversed. The seedling trees of the earlier settlers soon 

 reached reproductive maturity and furnished abundant seed for further 

 planting. The streets of the towns and villages were bordered with 

 the trees and the farmers who possessed prairie land planted groves 

 of them with the expectation of using the product for much- 

 needed fence posts, and for other purposes. But while the trees 

 were rapidly increasing in size by healthy growth, ominous reports 

 began to reach the settlers that the borer was moving westward and, 

 finally, that it was approaching the great region in which they had 

 made their homes. In due time the borers arrived there, for the in- 

 tervening country eastward had become so dotted with artificial groves 

 of the black locust tree that the insects in their beetle stage, easily 

 spread from grove to grove by natural flight. None of those trees in 

 the Mississippi valley had then reached the maximum size of the 



a A personal communication from Mr. A. E. Schwarz, of the U. S. Depart- 

 ment of Agriculture, who has long made special studies of the habits of these 

 insects, confirms my own observations as to the extent and imminence of their 

 ravages. He thinks, however, that the Locust borer possibly may not invade 

 our Pacific Coast region because the insect fauna there being so different from 

 that of which the borer is an original member is likely to prevent its geograph- 

 ical range over that region. He thinks it probable also that a similar faunal 

 influence has prevented the introduction of the borer into Europe, where the 

 tree has been so fully acclimated. 



