152 



The Colorado Beetle. 



numbers along the St. Joseph shore of Lake Michigan, where 

 they seem to have come by flying and swimming from the 

 opposite shore. 



Wind and water no doubt materially aid the advance of 

 this pest on the American continent, and no doubt would do 

 so here if the beetle became once permanently established. 

 Its spread over the greater part of America is, however, not 

 to be attributed to its power of flight, or to water, or wind, 

 but to artificial transportation. 



The beetles are carried by trains, boats, in barrels, amongst 

 the potato haulm, and even settled casually upon the wood- 

 work of a train or boat. Eggs may have now and then 

 been carried on living plants, and even pupae in earth, 

 but it is the adult beetle, with its great powers of vitality, 

 that has spread so rapidly through the agency of man. 



How can the beetle have made its journey to Great Britain r 

 We know that the adults can live for some time, and that, 

 too, without food. Nothing is easier for these beetles, which 

 swarm in America, and which have been seen flying about 

 in the streets of New York, to settle upon some outward- 

 bound vessel, and so be transferred to our shores. If that 

 insect happened to be a pregnant female, and met with favour- 

 able weather on reaching the Thames, she would soon fly to 

 the numerous neighbouring potato fields, lay eggs, and so 

 set up a colony. The strange thing is that it has not taken 

 place before. In no other way is it likely to have come over. 

 Potato haulm is not allowed to be imported from America, 

 under the Customs Order of 1877, so that there is no danger 

 of its introduction in that way, which would probably be a 

 fruitful source of infection. 



Pupae might be imported in particles of earth attached to 

 potatoes, but American potatoes generally come over in a 

 particularly clean condition, so that the chances are strongly 

 against invasion in that way. 



The Possibilities of the Beetle L iving in Great Britain, 

 Although we have no members of the genus Doryphora 

 living in Europe, there seems no reason why this particular 

 species should not live and become perpetually established. 

 The climatic conditions of this country are by no means 



