142 CHAPTER II 



the alpine region, others moorland and sandflats at a lower altitude, or native 

 meadows, including the epilittoral zone of lakes or the sea. In the maritime pro- 

 vinces of Canada, however, a notably high number of Amara species is restricted 

 to cultivated ground, waste places, &c., to the "culture steppe". From Labrador, 

 Newfoundland, and Nova Scotia, 24 species of Amara are known altogether; 13 

 of these inhabit ground more or less untouched by man, as just described, only 

 one, Amara fulva DeG., being a recent introduction. The remaining 11 are bound 

 to waste ground or arable land or at any rate are clearly favoured by human culture; 

 of these 6 are European introductions {A. aenea DeG., apricaria Payk., aulica 

 Panz., hifrons Gyll., familtaris Dft., lunicoUis Schio.) and only 5 indigenous to 

 North America {A. avida Say, impuncticolUs Say, latior Kby., pallipes K.hy.,pat- 

 ruelis Dej.). 



4. THE BIOLOGICAL CRITERION. The natural history of a species may preclude 

 any idea of regarding it as indigenous. This evidence is very strong in plant-feeders 

 and parasites monophagously bound to a single host. The Colorado beetle {Lep- 

 tinotarsa decemlineata Say) was unable to live in Europe before the cultivation of 

 potatoes was started in the late i6th century and the same applies to several pests 

 of Citrus trees in North America before the introduction of their hosts. The weevils 

 [Curcidionidae) and other insects feeding on various species of clover (Trifolium) 

 in eastern Canada and northern New England had no indigenous host at their 

 disposal until the transatlantic trade started. 



5. THE TAXONOMic CRITERION. This is especially valuable in cases where a 

 species occurs on a continent partly as indigenous, partly as a result of recent in- 

 troduction. In certain cases the two forms may be taxonomically separate, even 

 if the distinguishing characters are of less than subspecific value. The form of the 

 lady-bird Cocciriella ll-punctata L. occurring on the Pacific coast of North America 

 (as far north as Alaska) has been separated as a subspecies or variety, menetriesi Muls., 

 and is probably indigenous. The same species on the Atlantic coast is not distin- 

 guishable from the European forma typica and is no doubt a late introduction. A 

 taxonomic separation may also be possible between one indigenous and one intro- 

 duced form of the Carabid beetle Amara lunicoUis Schio. 



Due to subspecific difi"erences it can also be proved that Carahus granulatus L. 

 (fig. 8) has been introduced at least twice into the North American continent. Nova 

 Scotia and New Brunswick are inhabited by the sbsp. hibernicus Lth. which in 

 Europe seems to occur in unmixed populations only in Ireland (Lindroth, 1955b), 

 and it therefore certainly originated from this island. In other parts of eastern 

 North America, as well as in the Pacific Northwest, granulatus is represented by 



