196 



CHAPTER II 



per cent 

 100t 



Number of specimens 

 11—20 21—40 /11— 60 61—80 



DIAGR. 4. Abundance groups of the 64 species of Carabid beetles found on waste 

 ground (A, table 5) on 7 ballast places in SW England. 

 Black = "emigrants". White = non-emigrants. 



Of these all but one (Amara plebeja) occur in North America as "emigrants". 



If both frequency and abundance are considered, both on a 6 degree scale (as 

 in diagr. 3 and 4), it appears that of 16 species topping the list 11 are "emigrants". 



It certainly cannot be regarded as presumptuous to declare that the composition 

 of the Carabid fauna, especially of its "emigrant" element, on the ballast-places 

 investigated strongly supports the idea of a ship transport of the said element 

 across the Atlantic. 



Still more pronounced is the geographical composition of some other of the col- 

 lected groups of animals: 



Of 37 species of Curcidionids 12 are "emigrants" = 32 per cent 



,, 18 ,, ,, Molluscs 9 ,, ,, — 50 ,, ,, 



,, 23 ,, ,, "Iso-Myriapods" 19 ,, ,, = 83 ,, ,, 



On the other hand, the ballast material contains only few species of Hemiptera 

 Heteroptera and Araneae in common with North America (for explanation, vide 

 below, p. 199). 



The plants 



Without any pretensions to completeness, the more abundant or otherwise 

 conspicuous vascular plants of the ballast-places were noted. The identification of 

 some critical species was made or controlled by Mr. K. A. Mattisson, Botanical 

 Institute, University of Lund. The complete list of observed species, divided into 

 the three types of investigated localities, follows here: 



