BY PLANTS AND VEGETABLES 459 



stunt and deform the whole plant. The order of its going 

 I know not, but this Aphis has travelled to the ends of 

 the earth, probably from Europe where it is widespread and 

 abundant. Southwards it has made a home in Africa, furthest 

 east it is known in Japan, furthest west in Canada and the 

 United States, and it has reached the isles of Hawaii in the 

 midst of the Pacific Ocean. 



Butterflies, Two-winged Flies, and Plant-bugs the 

 cabbage and its kind disperse them with equal impartiality, 

 but occasionally an unlooked-for alien is smuggled in under 

 the mantle of the cabbage leaves. In this way a couple of 

 young Land Snails {Achatinafulica) were brought to Ceylon, 

 and were thrown unwittingly into a garden. These refugees 

 grew in size and multiplied, their descendants spread from 

 their garden into other gardens and over a district, peopling 

 in 1910 an area of three or four square miles with incredible 

 numbers. In spite of the fact that a fully developed Achatina 

 fulica has a shell 4^ inches long, shaped like a " Buckle " or 

 Dog-Whelk, 375 of these pests were counted in a garden 

 in a space of four yards square, 227 were found in a single 

 cluster on a coconut tree, and millions in all could be seen 

 crawling upon the ground, or climbing walls, poles or the 

 trunks of trees. They did little serious damage, but serve 

 to prove the influence of the cabbage as a smuggler. 



Many an old-established vegetable is accompanied in its 

 travels by its own peculiar camp-followers. Asparagus has 

 carried the European Asparagus Beetle (Crioceris asparagi], 

 a red, yellow and black pest which devours the crowns of 

 young plants, to Canada and the United States, as well as 

 to the Argentine, in all of which countries it has become an 

 established nuisance. And so with many other vegetables 

 and their pests ; but enough has been said to show the effects 

 of a mode of transference, the operations of which in Scotland 

 have been obscured by the passing of time. 



TYPES TRANSFERRED BY NURSERY STOCKS 

 AND LIVING TREES 



Stocks and trees, like vegetables, have their own peculiar 

 population : it is remarkable how large a proportion of the 

 creatures introduced to new countries through the agency 

 of living trees, belongs to groups of Plant-bugs the 



