24 MIGRATION, DISTRIBUTION, ACCLIMATISATION, ETC. 



other places. Many of the species living here under 

 glass are far more injurious in the open air, in sub- 

 tropical and other countries, than they are in the 

 artificially heated plant-houses in this country. Of 

 these we may quote the injurious " mealy bugs " 

 (Dact'i/lopius, spp.), which, even as near home as 

 Southern Europe, are destructive pests to orange trees 

 and a host of other plants. 



The occurrence of certain species of Coccidsin coun- 

 tries so widely separated and so completely isolated 

 has undoubtedly been brought about by the importa- 

 tion of plants, which is now so rapidly carried on in 

 all parts of the world. The fixed, inert character of 

 the Coccids, the minute size of their larvae, render them 

 the easiest of all insects to be carried long distances ; 

 and what is equally important, on their arrival in a 

 new country they may easily escape the eyes of the 

 untrained horticulturist, who, although he may be 

 " dead on all scale and bug," would be unable to detect 

 the almost microscopic young which might be lurking 

 in a hundred places. To take a case in point, I will 

 quote my observations on the introduction into this 

 country of a Japanese Coccid (' Gardener's Chronicle,' 

 vol. xxiv, pp. 245, 246) : " In January of the 

 .... year (1898) a consignment of several hundred 

 Japanese cherries (Prnnus pseudo-cerosus) was im- 

 ported into this country from Japan, which ultimately 

 fell into many hands, and were disseminated over the 

 British Isles without any knowledge they were badly 

 infested with ' scale.' In the following April two of 

 the plants from the consignment were submitted to 

 the writer for the purpose of identifying the insects 

 upon them, which proved to be the destructive Diaspis 

 amygdali of Try on." * 



On inquiry it was found that the greater number of 

 plants of this particular batch (100) had been planted 

 out of doors since the time of their arrival, and, as the 

 examination proved, the insects were not in any way 



* Now considered a syn. of Diaspis (aulacaapis) pentagona, T. T. 



