66 SCIENCE PROGRESS 



be said to be definitely known. Most probably it came from 

 Northern China, where it has been recognised so long that there 

 is no record of its origin. It did not call for much comment 

 there, because it was held in check by its natural enemies. The 

 introduction of one of these enemies (a lady-bird beetle) into 

 America has not had the same good results as the Australian 

 Vedalia, partly because the beetles themselves were attacked by 

 a parasite. 



The actual introduction of the San Jose Scale into America 

 seems to have been made from Japan, on some Japanese plums 

 sent to California with the hope they would prove Cuculio- 

 proof. From California it was sent with nursery stock to Penn- 

 sylvania in 1890 and 1891, and also to Virginia and a few other 

 Eastern States. From that time it has gradually spread over 

 America until it now does millions of dollars' worth of damage 

 every year. So important is this pest that not only most of 

 the American States, but most of the European countries, have 

 laws safeguarding them against its introduction — even Turkey. 

 Britain stands alone in not fearing the advent of this pest ! 

 There is no reason why it should not flourish in the West of 

 England just as it does in Canada. It occurs also in Australia. 

 Not only may it be spread by means of nursery stock, but also 

 on fruit, especially apples and pears. 1 It also infests countless 

 hardy plants, trees, shrubs, and vines. 



Thus in three ways we see how insects have been spread 

 from one country to another by artificial means — namely, on 

 stems of plants, in and on fruit, and in packages. There is yet 

 a fourth way — namely, on the roots. 



The Woolly Aphis {Schizoneura lanigera); or, as it is wrongly 

 called, the American Blight, not only lives on the trunk and 

 twigs of apple and pear, but also on the roots, where it produces 

 galls of a similar form to those above ground. This woolly aphis 

 lives during winter in two ways — (1) as active insects hidden 

 in crevices in the bark, both above and below ground, and (2) 

 as eggs, which are few in number and which are placed close 

 to the base of the stem. It is extremely difficult to see a few 

 of these insects or ova during the winter, when they are hidden 

 away. As no steps were taken formerly to check insect intro- 

 duction into our colonies and America, it is not surprising to 

 find this Schizoneura wherever apples are grown. It abounds 

 1 This is doubted by many of the chief authorities in America. 



