2 Introductory. 



will be quite free. Similarly, a coffee or tea bush, sheltered by 

 some overhanging rock, will usually be more subject to ' Red- 

 spider,' ' Mealy-bug,' and ' Scale,' than are more exposed trees. 



It is a curious fact, in connexion with Scale Insects, that 

 particular species are liable — under certain circumstances, such as 

 the accidental extermination or reduction of some natural enemy— 

 to suddenly spring into prominence. Another great source of 

 danger is the introduction of new species from other countries. 

 This may easily happen with the importation of foreign fruit and 

 growing plants. I have myself seen living specimens of the 

 mussel-scale' {Mytilaspis pomoruni) upon Tasmanian apples sold 

 in Ceylon. In California and some other American states a 

 special quarantine officer is appointed, whose duty is to examine 

 all importations of plants and fruit, and to disinfect or destroy any 

 infected stock. It is extremely probable that the Green-bug 

 {Lecaniuvi viride) was an introduction, though its original home 

 has never been determined. The Orthezia {0. insignis) that 

 suddenly appeared in the Botanical Gardens, Peradeniya, was 

 certainly brought into the country with living plants. 



To show the exceptional danger of introduced pests, I cannot 

 do better than quote from the very excellent report for the year 

 1895 of the Government Entomologist (Mr. C. P. Lounsbury), at 

 the Cape of Good Hope. On page 14 he writes : — 



' The increased destructiveness of imported insects is well 

 known. Few insects in this country now demand greater attention 

 than the Phylloxera of the Vine. In the Eastern United States, 

 the original home of this insect, it is rarely heard of as injurious, 

 but, throughout those countries into which it has been unfortunately 

 introduced, its terrible destructiveness, under new and more favour- 

 able conditions, has manifested itself. Another almost equally 

 striking illustration in Cape Colony is the Australian bug ijcerya 

 purchasi, Mask.). In Australia its ravages are never very extensive, 

 but its depredations in this country will not soon be forgotten. 

 The increased ravages of injurious insects in new countries result 

 from the improved conditions under which they become placed. 

 The relations which have existed, perhaps for centuries, between 

 them and their food plants, their parasites and predacious enemies, 

 such as other insects and birds, are all suddenly broken. In their 

 importation their natural enemies, which had previously preserved 

 a balance between them and the vegetable world, are all left 

 behind, and they are free to increase and multiply without hindrance 



