BIOLOGY. 293 



On the other hand, we see a species, only introduced into this 

 country from Europe some 12 years ago, which has already 

 almost put a stop to the cultivation of the gooseberry and red cur- 

 rant throughout a large part of the State of New York, the north- 

 ern borders of Pennsylvania, and the whole of Canada West, and 

 -is slowly but surely extending itself in all directions from the point 

 where it was originally imported. What can be the reason of 

 such a wide difference in the noxious powers of two such closely 

 allied insects, feeding on exactly the same plants, but one of them 

 indigenous to America and the other imported into America from 

 Europe? Nor is this the only case of the kind. We can point 

 out at least three other such cases. The imported onion-fly (An- 

 tliomyia cepanim) is a terrible pest to the onion-grower in the 

 East, though it has not yet made its way out West. On the other 

 hand, the native American onion-fly (Ortalis arcuata, Walker), 

 which is a closely allied species and has almost exactly the same 

 habits, has only been heard of in one or two circumscribed local- 

 ities in the West, and even there does comparatively but little dam- 

 age. Again, the imported oyster-shell bark-louse (Aspidiotus conchi- 

 formis) is a far worse foe to the apple and certain other fruit-trees 

 than our indigenous Harris 1 bark-louse (Asp. Harrisii), though 

 each of them infests the same species. Finally, the imported 

 meal-worm beetle (Tenebrio molitor) swarms throughout the whole 

 United States, and is a great pest; while the native American, 

 species (Tenebrio obscurus), which has almost exactly the same 

 habits, belongs to the same genus, and is of very nearly the same 

 size, shape, and color, is comparatively quite rare among us, and 

 is scarcely known to our millers and flour-dealers. 



On a careful and close examination, it will be found that almost 

 all our worst insect foes have been imported among us from the 

 other side of the Atlantic. The Hessian fly was imported almost 90 

 years ago ; the wheat niidge about half as long ago ; the bee moth 

 at the beginning of the present century ; the codling moth, the 

 cabbage tinea, the borer of the red currant, the oyster-shell bark- 

 louse, the grain plant-louse, the cabbage plant-.louse, the currant 

 plant-louse, the apple-tree plant-louse, the pear-tree flea-louse, the 

 cheese-maggot, the common meal-worm, the grain-weevil, the 

 house-fly, the leaf-beetle of the elm, the cockroach, the croton 

 bug, and the different carpet, clothes, and fur moths, at periods 

 which cannot be definitely fixed. Even within the last few years 

 the asparagus beetle has become naturalized in New York and 

 New Jersey, whence it will no doubt spread gradually westward 

 through the whole United States, while the rape butterfly was in- 

 troduced about a dozen years ago, and is rapidly spreading over 

 some of the Eastern States. And only a year ago the larva of a 

 certain owlet-moth (Hypogymna dispar}, which is a great pest in 

 Europe, both to fruit-trees and forest-trees, was accidentally in- 

 troduced by a Massachusetts entomologist into New England, 

 where it is spreading with great rapidity. It is just the same 

 thing with plants as with insects. We have looked carefully 

 through Gray's "Manual of Botany," and we find that ex- 

 cluding from consideration all cryptograms, and all doubtful 



