4 6o ANIMALS INTRODUCED UNAWARES 



Greenflies and the Scale Insects. I have already mentioned 

 the Mussel Scale as having benefited by the traffic in apples, 

 but in-all likelihood the trees are more to blame for its spread 

 than the fruit. An equally clear case is that of the Mulberry 

 Scale, called because of its shape, Aulacaspis pentagona, a 

 pest upon great variety of trees and shrubs. The female 

 Scales are unable to fly, and the larvae can move only a short 

 distance, so that what progress the species has made in its 

 distribution is due to the interference of man. Supposed 

 originally to have belonged to Japan, it is now found in 

 all tropical or warm temperate lands : throughout southern 

 Europe, in Africa, in Canada and the United States, in 

 Brazil and the Argentine, in Australia and in the lesser 

 islands West Indies, Seychelles, Zanzibar. There is no 

 doubt as to the means of its dispersal : it has actually been 

 intercepted over and over again in the act of being smuggled 

 into the United States and the isles of Hawaii upon the 

 stems of trees and shrubs. In 1898 it was introduced to 

 Britain on a consignment of several hundred Flowering 

 Cherry trees from Japan, and these were distributed through- 

 out the country before the presence of the pest was discovered. 

 Change of climate seems to have no ill effect upon the inter- 

 loper. 



The progress of the naturalization of such alien immi- 

 grants can often be traced. The Camellia or Cottony Scale 

 {Pulvinaria floe cif era), a traveller of cosmopolitan experience, 

 found in British glasshouses, cool or warm, has only recently 

 been imported to California, although it is common in the 

 eastern and southern regions of Canada and the United 

 States, and in the western State it has so far obtained foot- 

 hold only in a single locality near San Jose. 



Scale Insects undoubtedly owe their wide distribution to 

 the smallness and insignificance which enables them to elude 

 observation. Where no system of expert examination of 

 imported plants is in force, the introduction and establish- 

 ment of injurious Scales may, under the conditions of modern 

 commerce, be absolutely relied upon. Britain, with her lofty 

 disregard of the benefits of a humble science, reverses the 

 old saw, and prefers the cure to prevention. As a result, 

 there has been added to her fauna during the present gene- 

 ration, and this is only one of the items, a long series of 



