58 



SCIENCE. 



[Vol. XXI. No. 522 



Starting in Colorado, it pushed its way rapidly eastward to the 

 Atlantic coast, and, though not confined to our north-western 

 route, as we have termed it, nevertlieless, its most rapid progress 

 and greatest destruction was executed north of our imaginary 

 line. Even yet it has not spread southward to the Gulf of 

 Mexico. 



■ Another species ot whose advance I am not so certain, is Dia- 

 brotia longicornis Say, described many years ago from examples 

 collected near the foot of the Rocky Mountains, but which I know 

 to now occur in Arizona and Central America. This has become 

 a terrible pest in fields of Indian corn all over the west; and Pro- 

 fessor Forbes Of Illinois, some years since, expressed the opinion 

 that it was moving eastward. While mentally differing from 

 this opinion myself, yet the fact that it has, this year, been re- 

 ported for the first time in Ohio, along the western border, has 

 led me to feel that Professor Forbes' opinion may yet prove to be 

 a correct one. Certainly we shall watch and mark its progress 

 carefully. Its congener, Diabroiica Vi-punctata Oliv., though we 

 do not know it to be of southern origin, yet it is very destructive 

 to the same cereal in the south, but this injury, so far as known, 

 is confined, largely at least, to the territory south of the dividing 



Diarraea, along the Atlantic, remains yet to be seen. They are 

 both slowly making their way along our great south-western high- 

 way, and if either reach Ohio it will most likely be theDiatrseaand 

 along our southern border. The Harlequin Cabbage Bug, Mur- 

 gantia histrionica Hahau, is known to occur as far south as Guate- 

 mala, through Mexico, and first came to notice in destructive num- 

 bers in Texas about 1866. Four years later, it had pushed north 

 to Missouri, and in 1875 it had made its way to Delaware, and on 

 the west occupied wholly or in part Arizona, Nevada, Califor- 

 nia, Indian Territory and Colorado. It is now found in extreme 

 southern Illinois, Indiana and Ohio, in all cases, I believe, near 

 the dividing line between the two routes, also in New Jersey, 

 thus covering almost exactly the south-western highway, but, 

 excepting, perhaps, in the far west and near the Atlantic, not ex- 

 tending far beyond it. Although an older established species, 

 Dynastes tityus Linn, occupies almost exactly the same area ex- 

 cept in the extreme east, where Dr. Lintner has recorded it at 

 Kingston, some seventy miles north of New York City. To my 

 personal knowledge it breeds in southei'n Illinois, and also at 

 Bloomington, Indiana. I have found it at Columbus, Indiana, 

 and have good evidence of its occurrence in the vicinity of Co- 



Map indicating, approximately, the natural divide between tlie northern and southern insect fauiias, 

 east of the Rocky Mountains. 



line, unless it be in Ohio, where, I strongly suspect, it is more de- 

 structive than we are aware. Of the south-west route, we have 

 already observed much in relation to such species as have pushed 

 their way over it from the east toward the south-west. There- 

 fore, I shall speak only of such species, with two exceptions 

 American, I believe, as have passed over the ground from south- 

 west to north-east. One of these exceptions is the larger corn- 

 stalk-borer, Diatrcea saccharalis F. 



According to Mr. L. O. Howai'd, who has studied the species 

 quite thoroughly, it may be a native of the West Indies, or it may 

 have originated in South America and made its way to the United 

 States by way of these islands. Be this as it may, it occurs along 

 the Gulf and Atlantic coasts, and, in the light of recent observa- 

 tions, it seems to be pushing its way northward along the Atlan- 

 tic, having now reached the vicinity of Washington, D. C. 

 Though for years known to infest both sugar-cane and maize, in 

 Louisiana, yet we have no information of a corresponding advance 

 northward. This, in some respects, appears to be the case with 

 another insect, Gylas formicarius Fab., which breeds in the sweet 

 potato, a native of Cochin China, India and Madagascar, but in- 

 fcroduced into the United States, probably, by" way of Cuba. 

 This may have been first introduced either into Florida or Lou- 

 isiana, as it occurs in both States, and is now pushing its way 

 west across Texas. Whether it will follow in the path of the 



lumbus, Ohio. It has been known from southern Pennsylvania, 

 and, later, from New York. Of the Bag or Basket-worm, Tky- 

 ridopteryx ejiJiemej-ceformis Haw., also a southei'n species, I only 

 know that it breeds in southern Illinois, Indiana, and in Ohio, a 

 short distance north of Hamilton, Butler County, while under At- 

 lantic influences, it is sometimes abundant as far north as New 

 York and found also in Massachusetts. The Praying Mantis, 

 Stagmomantis Carolina Linn., breeds in extreme southern Illinois, 

 and also in extreme southern Indiana, but is said not to do so in 

 Ohio. I have a male, given me some years .'^ince by Professor S, 

 S. Gorby, State Geologist of Indiana, that was captured in a rail- 

 way coach, running between Cincinnati. Ohio, and Indianapolis, 

 and was captured between the latter city and Dayton, Ohio. I 

 also learned that this summer a female was captured in Indian- 

 apolis, by which I judge that these two southern species are 

 hovering in the vicinity of our boundary line. 



As before stated, we have used as examples species of economic 

 interest, only for the reason that their movements are better 

 understood. A careful study of the geographical distribution 

 of other species would, doubtless, throw more light upon the 

 problem. Our dividing line is supposed to be correct only in a 

 general way, as, of course, there can be no such thing as an ex- 

 act or continuous line of demarkation. This will of necessity be 

 more or less irregular. Again, a species spreads over an area 



