_References on habitats and trails._--J. B. Tyrrell, 1892: 129, and 1895: 445; W. J. McLean, 1901: 6; Blanchet, 1925: 33, and 1926a: 73, 96-97; Mallet, 1926: 79, 80; Seton, 1929, +3+: 100-102, 122, 127-128; Jacobi, 1931: 186-187; Ingstad, 1933: 86; Murie, 1939: 246; Manning, 1948: 26-28; Rand, 1948a: 212; Harper, 1949: 226, 228; Banfield, 1951a: 3. _Influence of weather on distribution_ In the section on _Migrations_ the meteorological conditions in 1947 have been reported for any possible bearing they may have had on the daily movements of the Caribou, particularly during the fall migration. The temperature has an important effect on the activity of the insect pests (see _Influence of insects on distribution_) and thus, to a certain extent during summer and fall, on the behavior and probably the distribution of the Caribou. Low winter temperatures on the Barren Grounds do not appear to be a factor of prime importance in the seasonal distribution of _R. a. arcticus_. “Some individuals and small herds remain in the northern part of the range at all seasons” (R. M. Anderson, 1947: 178). Peary’s Caribou (_R. pearyi_) inhabits the more northerly Arctic islands throughout the year, without engaging in such extensive migrations as its relative to the south. The forceful winds that blow over the Barren Grounds so much of the time are of distinct benefit to the Caribou during the summer in abating the very serious scourge of flies. If other things were equal (as they are not), this factor alone would make the Barrens a more favorable summer habitat than the forested country. (See _Retrograde autumnal movement_.) Air movements of similar strength during the winter must, through the wind-chill factor (_cf._ Siple and Passel, 1945), make life so much the harder for any living being; on the other hand, they tend to sweep the ridges bare of snow, thereby making readily available the Caribou’s principal winter food of reindeer lichens (_Cladonia_ spp.) _References._--Armstrong, 1857: 479; Critchell-Bullock, 1930: 192, 194-196; Hoare, 1930: 33; Jacobi, 1931: 193, 195; Clarke, 1940: 96, 99; Banfield, 1951a: 27-29. _Influence of food supply on distribution_