HEARINGS BEFORE COMMITTEE ON AGRICULTURE. 289 
sion, and where it can be combated or avoided by notifying the farm- 
ers In advance. Similarly with yellow fever. Investigations have 
recently shown that the yellow fever is strictly confined—-the breeding 
of the yellow-fever mosquito—to the austral riparian region here, this 
lower transcontinental belt, to humid parts of that region; and yellow 
fever does not occur outside of that, and that is a matter of enormous 
practical importance to the people of the United States. It is so in 
the spread of many diseases of cattle, that they are limited by these 
definite regions. 
Mr. Grarr. How do you ascertain about what particular grains or 
fruits grow in certain localities by the location of these wild animals 
and birds? 
Mr. Merriam. We find the area where a particular crop does best, 
and then we find additional areas where it does well, and that shows 
us at once, by platting them on our map, in what part of a zone or 
area this crop flourishes best commercially; and we know then that it 
is adapted to that zone, where conditions of equal humidity occur, and 
favorable soils, that it can be grown in that zone. We find sometimes, 
that in certain kinds of crops which have a wide latitude, they do 
fairly well in two zones; like the sugar beet, which does well in the 
transition belt—the belt colored blue on this map. That is its natural 
and best home, and it also thrives in the adjacent belt of upper Sonora. 
It does best in the boundary between the two. 
Mr. Scorr. These conclusions of yours have been reached by an 
examination of the growing crops? 
Mr. Merriam. Of the growing crops. 
My. Scorr. And by weather conditions too? 
Mr. Merriam. Yes; by study of climatic data of the temperatures 
and humidity and of the actual crops which are a success in definite 
places—a commercial success. We do not mean the things that have 
to be nursed and cuddled, but the things that do best in the open. 
Mr. Grarr. Mr. Scott remarked just now, asking if animal life had 
anything to do with it; I understood you to say it did a little while 
ago. 
ae Merriam. It does; certainly. Animal life and plant life coincide 
in their distribution. Where you find a certain species of animals you 
find certain species of plants, right across the country. You find cer- 
tain trees and shrubs in each of these belts that do not occur in other 
belts, in association with certain birds and reptiles. Where they recur, 
we know the crops that do best in the area will do quite well in other 
areas where soil conditions are suitable. So, in mapping these animal 
life areas we are mapping the agricultural belts, and we make a study 
of the crops throughout the belts, and publish lists of those that are 
adapted to each area and each subdivision of an area. 
Mr. Apams. Is not this one-hundredth meridian here a pretty arbi- 
trary line on your map? 
Mr. Merriam. That is a transition between the aridand humid. It 
is a somewhat irregular line, but it is a well-known line of division. 
Mr. Henry. Your investigations are originally with animal and 
vegetable life? 
Mr. Merriam. Yes; we study both together. 
Mr. Henry. To what extent, if at all, does the work of your division 
conflict with or supplement the Bureau of Soils and the Bureau of 
Plant Industries. 
CA 19 
