12 SCIENCE PROGRESS 



years we know. Some growers at one time even maintained 

 that the " Big Buds " were signs of increased vitality. The 

 importation of such diseased plants into any new district has 

 always been followed by the disease spreading out around the 

 infected plantation by natural means. The minute acari are 

 carried about by bees and birds. They are also spread artifi- 

 cially around an infested plantation by means of the baskets in 

 which fruit is picked, by the clothing of the pickers, and even 

 with the mud on people's boots. 



The Colorado Beetle {Doryphora decemlineata, Say.) has 

 been distributed artificially to this country, and there is not 

 the least doubt that if it had not been rigorously stamped out 

 by the authorities of the Board of Agriculture, acting under 

 the Colorado Beetle Order of 1877, it would have spread to 

 a disastrous extent. First it was found breeding luxuriously in 

 Tilbury Dockyard in 1901, and continued until 1902, in spite 

 of most drastic measures. In the latter year it was effectually 

 stamped out. 



The spread of this beetle by natural means has been remark- 

 able. Originally it lived on wild solanaceae in the Rocky 

 Mountains ; but as settlers pushed forward with their patches 

 of potatoes, the beetles left the wild plants for the cultivated, 

 and so spread farther and farther afield until now it is found 

 flying in the neighbourhood of New York, and has even been 

 seen in the city. How it was conveyed to England we do not 

 know, but probably some specimens flew on to a ship and left 

 it again on arrival at Tilbury. 



The Hessian Fly {Cecidomyia destructor, Say.) is another 

 instance showing the great harm caused by the introduction 

 by artificial means of an injurious insect into a new country. 

 There is plenty of evidence to show that this corn pest is 

 European in origin. It attacks not only cultivated graminaceae, 

 but also wild kinds. We hear, for instance, of it devastating 

 " twitch " or " couch " grass in Siberia. We know it occurs 

 on the same and on other grasses in Britain. One heard so 

 much of the Hessian Fly in the papers in 1891 that one was 

 brought to believe that it had been imported into this country 

 from America. In reality the insects were imported into 

 America with straw by the hired Hessian troops, and first took 

 up their abode at Long Island, and have gradually spread over 

 the greater part of the wheat-growing areas of North America. 



