VIII. i 



HANGERS-ON OF MAN AND HIS 

 DOMESTIC ANIMALS 



THE accidental importation of animals is of more funda- 

 mental importance in the make-up of our fauna than would 

 at first seem possible or probable. It is difficult to realize, 

 for example, that the parasites of man and of his domestic 

 animals have been distributed to the ends of the earth 

 through the migrations of the human races, and that almost 

 all of these were absent from our fauna before the advent 

 of man. It is true, of course, that some of our modern 

 tormentors may have occurred naturally on one or other 

 member of the native fauna, and may have turned their 

 attention to man only after his appearance in this country. 

 The Human Flea (Pulex irritans] is a true parasite of the 

 Badger in Britain and man may have derived it from this 

 source. But there can be no doubt that the virulent Plague 

 Flea (Xenopsylla cheopsis], responsible for the transmission 

 of the deadly bubonic plague, which in the fifteen years be- 

 tween 1896 and 1911 caused over 7,000,000 deaths in India 

 alone, is an undesirable alien occasionally introduced into 

 our large seaports from the East. It is almost certain too 

 that some, at any rate, of the Fleas of the Brown Rat, of 

 domestic dogs and cats, and of poultry, animals which owe 

 their presence to the influence of man, have been brought 

 with their hosts from foreign lands. Just so the deliberate 

 introduction of the European Starling to Australia involved 

 the importation of a Fowl-Mite (Liponyssus dursa), which 

 proved troublesome to the human inmates of a house in 

 Sydney in which Starlings were nesting. 



It is unnecessary, as it is impossible, to trace the history 

 of the introduction of human parasites to Britain and Scotland. 

 Most have been so long established that their migrations, 

 like those of man himself, are lost in the mist of ages. But 

 a few cases may be mentioned to illustrate the general 

 theme. 



