85 



to show how many of our now thoroughly established species may have 

 been brought to the state in this manner. This much for the insect cur- 

 rent of migration that has passed over our great northwestern route. 



In regard to the southwestern route, while it may be said to cover a 

 smaller area of the State, it has, probably, brought a less number of species 

 of foreign origin, while of American species, it may have supplied the 

 state fauna with nearly an equal number. Any one who will take the 

 pains to look into the matter will be surprised at the number of southern 

 species that are hovering about in the vicinity of our dividing line, which 

 marks either their approximate northern limit of occurrence, or else their 

 northern limit of normal abundance. Among the Lepidoptera, Agraulis 

 vanillse, Linn., is a good illustration, as it covers almost exactly the south- 

 ern area and is found in Indiana only in one of the extreme southern 

 counties. Argi/nnis diana, Cram., is probably another example. On the 

 other hand, Papilio aja.r, Linn., and P. crespliontes, Cram., both southern 

 species, have pushed over and far beyond our line of demarkation. Indeed, 

 it seems probable that the former has reached farther north in western 

 New York than it has along the Atlantic. The same might be said of one of 

 the Orthoptera, Acridium americanum, IScudd. I have observed this rarely 

 in southern DeKalb county, northern Illinois, and quite abundantly in 

 southern Illinois, and know it to occur sometimes in exceedingly great 

 numbers in southeast Indiana. It pushes far north of our dividing line, 

 but is abundant only near or to the south of it. The following from 

 " Field and Forest," Vol. II., p. 145, Feb., 1877, will prove interesting in 

 this connection: 



"Acridium americanum. — Two correspondents, of the Department of 

 Agriculture, writing from Vevay, Indiana, about the middle of last Novem- 

 ber, reported the visitation in that place of an immense cloud of grass- 

 hoppers that literally covered the streets of the town. One of the gentle- 

 men observed, about 5 P. M., dense cumulo stratus clouds in the south- 

 west, gradually overspreading the sky ; at G o'clock the wind had risen to 

 moderate gusts, and within half an hour a rattling noise was heard against 

 the windows, like that of light hail. On opening the doors, grasshoppers 

 entered in immense numbers, covering the floors, furniture, clothing, &c. 

 The shower continued till 8 o'clock P. M., when the ground was thickly 

 covered, and the boys began to burn them, shoveling them into bonfires. 

 The specimen sent shows the insect to have been the Acridium americanum, 

 one of our largest American grasshoppers." 



