200 CHAPTER II 



The essential difference depends on the fact that almost no species from saline 

 localities (in the collected material only the Chrysomelid beetle Phaedon cochleariae 

 F.), artd no halobiontic (salt-demanding) species, were introduced into North 

 America. This may sound absurd but must be explained by the fact that the ballast, 

 at least as a rule, was not taken from the tidal zone (cf. above, p. 165). The 

 soil there was wet, heavy to handle, and eventually lost part of its valuable 

 weight; it was often muddy and difficult to clean out of the ship afterwards. 



4th column. There is no difference between phytophagous beetles (p) and species 

 requiring other kinds of food, the former group constituting 25 per cent 

 (17 species) of the "emigrants" and likewise 25 per cent (44 species) of the 

 remainder. 



5th column. A slight difference is found between polyphagous and oligo- or 

 monophagous species, that is those specializing on restricted kinds of food. The 

 former group makes 85 per cent (58 species) of the "emigrants", 79 per cent (137 

 species) of the remainder. One would have expected a clearer demonstration of the 

 fact that a more or less pronounced monophagy disfavours introduction over long 

 distances. Apparently the figures are not quite representative, as is clear from a 

 somewhat different calculation on Curculionids (below, p. 210). 



6th column. The constantly short-winged (brachypterous) species and those 

 occurring in both macro- and brachypterous individuals (dimorphic species) 

 (b and d of column 6) are better represented among the "emigrants", 32 per cent 

 (22 species), than in the rest, 25 per cent (44 species). Flightless insects no doubt 

 had more chance to stay onboard during the voyage, escaping the risk of being 

 blown into the sea. The Hemiptera, as a rule capable of flight in the adult stage, 

 and the true spiders (Araneae), most of which are able to ascend by "ballooning", 

 at least as young, are also very poorly represented among the introduced species. 

 It is characteristic that the only true spider both occurring in the English ballast- 

 material and regarded as a European introduction in the fauna of Newfoundland 

 (Hackman, 1954, p. 40), is Micaria pulicaria Sund., a pronounced ground-species 

 without the habit of ballooning, found on four of the eight investigated ballast- 

 places. 



yth column. Five of the species observed on the ballast-places are constantly 

 parthenogenetic {Amischa analis, and four species of Otiorrhynchus), only females 

 being known, and all of them have been carried over to North America. This is 

 another proof of the extraordinary advantage of this form of reproduction for the 

 dispersal of a species: for a single specimen, in any stage of development, to be 

 deposited in a suitable spot, is sufficient to colonize a new area! The parthenogenesis 

 in Coleoptera, with very few exceptions (Suomalainen, 1953), is combined with 

 polyploidy (increase of chromosome number) and possibly this in itself effects a 



