134 MASSACHUSETTS HORTICULTURAL SOCIETY. 



for by the severity of the preceding winter which, it is supposed, 

 killed the insects. 



Certain kinds of birds are fond of particular species of insects, 

 and if a large flock of these should pass through an infested 

 region at the proper time, a great diminution of that special insect 

 pest would be the natural result. 



Predatory insects and natural parasites are great aids in pre- 

 venting the too great increase of injurious species, sometimes 

 waging a war almost of extermination against them. Occasionally 

 bacterial or fungal diseases may cause widespread destruction 

 among insect tribes, as well as among higher animals. 



Sometimes we find one species of insect supplanting another 

 which had much the same habit and fed on similar plants. The 

 common White, or Cabbage, Butterfly (Pieris rapce), was first 

 landed from Europe, at Quebec, and as it has spread south- 

 ward and westward, the native Avhite butterflies have become quite 

 rare in luany regions. The imported Cabbage Butterfly itself is 

 not so abundant and destructive as it was at first, because its 

 numbers have been greatly reduced by a minute parasitic fly which 

 has followed it. 



In recent years the ravages of insects have become more and 

 and more noticeable, and have necessarily received greater atten- 

 tion from caltiA\ators. The destruction of the native wild plants 

 upon which indigenous insects originally fed ; the increased areas 

 under cultivation, and the consequent abundance of food supply 

 of certain kinds ; the improvement and diversity of cultivated 

 plants — are all factors which have constantly tended to attract 

 insects from their native waste places and woods, to our gardens, 

 field crops, and orchards. Very often, as our population has 

 increased, certain kinds of valuable insect eating birds and other 

 animals have become scarcer. 



With active immigration and importation, we must expect also 

 to receive and naturalize more species of those insects which are 

 natives of, and are troublesome in, other countries. 



Among the most conspicuous of such immigrants already settled 

 among us, and now well known in the different branches of horti- 

 cultnre and agriculture, we have the Codling Moth (Carpoca2)sa 

 pomonella), the Oyster-shell Bark-louse (Mi/tilaspis pomorum), 

 affecting the apple and other allied fruits ; the Fhited Scale (Icerya. 

 Purchasi), destructive to trees of the Citrus group, and others, in 



