57 



cially bad. In a short time be began to react. He bad catarrb and cough. 

 On account of his cough he wan inclined to be in the open air less and less 

 and to house himself more and more, the very things be ought not to do. 

 When I pointed out these things he promptly changed his mode of life and 

 the reaction ceased. He was again "healthy". 



It Is undoubtedly true that all now common weeds and pests and para- 

 sites and diseases were restricted at one time to certain localities, from 

 whence they have spread until they have become cosmopolitan. There are 

 many data regarding first appearances. In our annual Proceedings, for 

 instance, are a number of records for the first appearance of new plants 

 and new animals, new in the sense of not having been found here before. 

 The appearance of new diseases in the State is of course recorded in the 

 medical journals, but imperfectly. The subject of the coming in of new 

 pests and parasites and diseases is an important one and cannot be dis- 

 missed with a few brief paragraphs. I should like to give at least one 

 illustration relating to the common potato. 



The potato was carried^ from South America to Europe about the 

 middle of the sixteenth century, and subsequently brought to our country, 

 and now goes under the name of the Irish potato. Those of middle age can 

 recall how. until in the seventies, the Colorado potato beetle was never seen 

 in our potato fields. How this beetle came to us is an interesting story. - 



On the dry western plains there grows a species of spiny Solanum 

 (S. rostratum), a near relative of the potato (S. tuberosum).' This plant 

 has a parasite, the beetle now commonly known as the potato bug. The 

 plant grows very sparingly and that means that the beetle also occurs 

 sparingly. A little reasoning will show why. If the bugs became abun- 

 dant and would completely consume their food plant then they themselves 

 would perish for want of food. On the desert the plants are far apart and 

 many escape the attacks of the bugs and ripen seed, or if a single bug 

 reaches a plant it will not injure it enough to destroy it. 



Now when the common potato began its westward march it gradually 

 reached the home of this beetle. The beetle found the new species more 

 acceptable than the old and, since plants were close together, life conditions 

 became easy and (be potato beetle, now called the potato bug, at once in- 

 creased enormously jiiid traveled from one field to another, and in a short 

 time overran the whule I'nilcd States. I was suriirised when in (lerniany 

 to see the potato fields free froui the potato bugs; authorities there are on 



