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. Furthermore, 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 suggestions 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 intervening 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 personal communication from Mr. A. E. Schwarz, of the U. S. Department 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 geographical 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.
