cultivated in its native country ; the other stuck to its original 

 food, but might, for all we know to the contrary, have increased 

 its range as easily as the beetle. Another dreadful scourge, the 

 Phylloxera, had also spread alarmingly, through man's aid, dur- 

 ing past years ; and now the question comes up, might not the 

 Rocky Mountain locust also spread with the assistance of man? 

 May not the increasing wheat fields be an inducement for them ? 

 and may they not in time be able to adapt themselves to cir- 

 cumstances of climate, etc.? It was impossible to say what, 

 if any, limits were marked out for them. He instanced examples 

 of foreign plants, such as the Canada thistle, and several parasites 

 which were known to thrive in this country, and which are now 

 plentiful. He also instanced a Cuscuta, which suddenly came up 

 in several parts of Europe some years ago, and did considerable 

 damage to the lucerne fields. This plant was a native of Chili, 

 and was introduced into Europe with the so-called alfalfa seed, 

 and was a pest for ten or fifteen years. It has now entirely disap- 

 peared from Europe, but has suddenly appeared in Califor- 

 nia. Fifty years ago it had been believed that the cholera would 

 not reach Europe or America, and forty-five years ago, when it 

 did travel westward, that it would be excluded from high eleva- 

 tions ; but it has since attacked Switzerland, and spread widely 

 through Mexico. The geography of plants and animals was a 

 comparatively recent science. Longitude, latitude, altitude, and 

 all that we call climate, certainly do limit certain species, but 

 only the experience of many years can teach us what those limits 

 are for each individual kind. 



Mr. Riley, in reply, said that facts such as those cited by Dr. 

 Engelmann might be multiplied ad infinitum, and that he had 

 done much to record them. He insisted, however, that they had 

 little to do with the argument in point. The locust is omnivo- 

 rous ; it will feed even upon animal matter, and so it will not be 

 influenced by man's agency. There has been but little change in 

 the country, between here and the Rocky Mountains, as to locust- 

 food supply, and that country affords the locust no more nutri- 

 ment now than before settlement. By gradually spreading from 

 year to year, as the Doryphora has done, the species might con- 

 form to the new conditions, but the transition was sudden from 

 the high and dry climate of the locust's native home to the more 



