68 SCIENCE PROGRESS 



be carried over land and sea for any distance. It is surprising 

 that this pest has not made its way to other parts than America 

 before now. 



In a similar way we can account for the wide distribution of 

 the Pear and Cherry Sawfly, or Slugworm {Eriocampa limacina), 

 which exists in America and Cape Colony. The Slugworms 

 pass the winter in small earthen cocoons in the soil. They are 

 often very abundant on nursery stock, and some cocoons are 

 sure to be lifted with the stock and may remain attached to the 

 roots with small clots of earth. Taken to a fresh country, they 

 will hatch out in due course, unless the roots are previously 

 treated. 



As there is no doubt about the dispersal of such pests on 

 rootage, it is very important that all imported stock should 

 have the roots well cleansed before being planted. This is, I 

 fancy, a point generally overlooked, but one of great importance 

 in the artificial distribution of insect enemies. 



Just as with hexapods, so with Eriophyid mites. These 

 minute acari, formerly known as Phytoptidce, live either in buds 

 alone, as we see happens with the Big Bud Mite of the Currant 

 {Eriophyes ribis, Nalepa), or in galls formed on leafage and 

 blossom, as in the Pear-leaf Blister Mite (E. pyri, Sch.) and 

 the Cotton Mite {E. gossyperi) respectively. In the pear pest 

 the winter is passed in the buds, and the same applies to those 

 that gall the leaves of the plum. It is extremely difficult to 

 detect the presence in winter buds of the leaf-living forms, 

 as the invaded buds do not swell. On the other hand, we all 

 know the well-marked, swollen appearance of the " Big Bud " 

 attack in black currants. It is not surprising, therefore, to find 

 that the pear phytopt has a wide distribution. The Pear-leaf 

 Blister Mite {Eriophyes pyri) is now found in America, Canada, 

 and in Cape Colony. There is no doubt that it has been imported 

 into all three countries with nursery stock, grafts, etc. ; but we 

 have no evidence showing when this took place. In some of 

 its new environments this mite seems much more destructive 

 than it is in its original home. 



The Big Bud Mite of the Currant {Eriophyes ribis) so far does 

 not occur outside Europe, but its distribution there has increased 

 very rapidly. No natural causes can account for it. On the 

 other hand, we can do so by the distribution of infested stock. 

 That this has taken place in a most persistent manner for some 



