644 The American Naturalist. [July, 
greatest, while on the other hand the reds are distributed over 
the less favored parts of the country. Along the Atlantic and 
Gulf coasts, this humid belt corresponds very closely with the 
pine belt on map No. 5 (although narrower on the Atlantic 
slope) Here the distribution of the color phases fails to cor- 
respond with either the pine or the humid belt, although it 
does so perfectly with the temperature zones (see map No. 4), 
while in the northern part of the United States and in Canada 
the similarity is very great. Unfortunately, no data exist for 
the little strip extending down the Alleghanies, but as moun- 
tanious regions are, as a rule, exceedingly humid, particularly 
when heavily wooded, there is little doubt but that when data 
is collected for this region, it will show a narrow strip reaching : 
from New York State to the neighborhood of eastern Ken- 
tucky, when the similarity between color distribution, humid- 
ity, temperature and forest areas will be nearly complete. 
The whole subject of dichromatism as regards Megascops, 
may be considered a special case of the general subject of 
darker colored species inhabiting humid areas. The red form 
can be assumed to be a more highly colored form of the gray, 
and the same is true of Megascops as & whole in which 
the various subspecies — floridanus, ‘mccallii, kennicottii, 
bendirei, mazwelliz and trichopsis—are representative of the 
dark and light forms respectively of the humid and arid 
regions, and in Megascops asio proper, the gray may be taken as 
the form inhabiting humid areas, while the red phase repre- 
sents the lighter colored forms of the drier region. 
B.—INFLUENCE OF TEMPERATURE. 
According to Verrill and Allen,‘ the most potent of all influ- 
ences 1n the distribution of color is temperature, which, in the 
case of birds, is greatest during the breeding season, and as in 
the case of humidity, map No. 4 is based upon the data for the 
months previously mentioned. Now, by reference to map No. 4, 
-it will be seen that there are three belts or zones of temperature 
corresponding to the distribution of the red and gray phases of _ 
the screech-owl—the one reaching from Charleston, S. C., to 
*N. A. Fauna, No. 3, p. 26. | 
