ON THE BIO-GEOGRAPHY OF MEXICO, TEXAS, NEW MEXICO, 
AND ARIZONA, 
WITH SPECIAL REFERENCE TO THE LIMITS OF THE 
LIFE AREAS, AND A PROVISIONAL SYNOPSIS OF THE 
BIO-GEOGRAPHIC DIVISIONS OF AMERICA. 
BY C. H. TYLER TOWNSEND. 
During the past five years I have enjoyed the good fortune of having 
constant and abundant opportunities for making observations on the 
features and boundaries of the life areas in various districts throughout 
what is now known by Dr. Merriam as the Loioer Sonoran , in Mexico, 
New Mexico, Arizona, and Texas; the Upper Sonoran and Transition to 
the north, in New Mexico and Arizona; and the Tropical to the south, 
in Mexico and the West Indies. This paper is intended to record the 
more important of these observations, with the view of aiding in the 
solution of the difficult problem of the proper boundaries between these 
areas. It is well understood that the flora of these regions is of great 
importance in arriving at a correct sense of their limits. Further than 
this, the possibilities of the flora in an economic or agricultural sense are 
of prime importance. This paper therefore takes into consideration all 
pertinent »bservations on the flora, both introduced and native. In fact, 
it should be stated here that the native and economic flora and the me¬ 
teorology of the regions have been made large use of, in defining the 
limits of the life areas. It must also be stated that I have paid especial 
attention to the distribution of the insect fauna in the above mentioned 
areas, and that any available conclusions to be drawn therefrom are made 
use of, as well as significant facts relating to the vertebrate fauna. For 
a clearer understanding of these remarks, the reader is asked to compare 
them with Dr. Merriam’s admirable maps of the life areas of North 
America. (Second and third Provisional Bio-geographic Mays of North 
America. Washington: March, 1892, and December, 1893.) I wish 
only to add that, unless otherwise noted, I have personally visited all of 
the localities regarding which statements occur in the text, and thus 
speak directly from my own observations. A considerable part of the 
observations on Mexico, and most of those on Texas, were made inci- 
centally while engaged in the field under the Entomological Division of 
(71) 
