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Rh deeply into the tropical half of the country, carry with them temperate and sub-tropical conditions over much the greater part of the republic. Above the plateau rise the marginal sierras, while a few isolated peaks in the region of perpetual snow give to Mexico a considerable area of cold temperate and a trace of arctic conditions. Descending to the lowlands on either side of the plateau, the temperature rises steadily until the upper limit of the tropical region, called tierras calientes, is reached, where the climate is hot, humid and unhealthy, as elsewhere in the forested coastal plains of tropical America.

The tierras calientes (hot lands) of Mexico include the two coastal zones, the Isthmus of Tehuantepec, the states of Tabasco, Campeche, and part of Chiapas, the peninsula of Yucatán and a part of eastern Oaxaca. The mean temperature ranges from 77° to 82° F., seldom falling below 60°, but often rising to 105°, and in the sultry districts of Vera Cruz, Guaymas and Acapulco to and even above 110°. The rainfall is heavy in the south, except Yucatán, but diminishes gradually toward the north, until on the Pacific and Gulf of California coasts it almost disappears. These lowland districts are densely forested in the south, except Yucatán, and large areas are covered with streams, swamps and lagoons, the abode of noxious insects, pestilential fevers and dysentery. On both coasts yellow fever epidemics appear at frequent intervals. The great fertility of these regions and the marvellous wealth of their forests are irresistible attractions to industrial and commercial enterprise, but their unhealthiness restricts development and is a bar to any satisfactory increase in population. The heavy rainfall on the Gulf coast, however, which reaches a maximum of 90 to 100 in. in the Huatusco district of Vera Cruz, causes the flooding of large areas of lowlands, and will make improvement very difficult. The peninsula of Yucatán, whose general level does not rise above 130 to 200 ft. above the sea, consists almost wholly of an open, dry, calcareous plain. The temperature ranges from 66° to 89°, but the heat is tempered by the cool sea-breezes which sweep unobstructed across its plains. The rainfall is abundant in the rainy season, but in the long dry season it is extremely rare. In the wet season the rain is quickly absorbed by the dry, porous soil; consequently there are no rivers and no lakes except near the forested region of the south-east. These exceptional conditions give to Yucatán a moderately hot, dry, and comparatively healthful climate. Another hot, dry climate is that of the tierras calientes of Sonora. The coast is low and extremely arid, and would be uninhabitable were it not for the proximity of the Sierra Madre, where a light rainfall is experienced, and for the numerous rivers that cross the arid belt between the mountains and the sea. The maximum temperatures in this region are 98° at Hermosillo and 119° at Guaymas.,

To a large extent the climate of Mexico is determined by vertical zones. According to H. H. Bancroft (Resources of Mexico, pp. 3–4), the tierras calientes, which include a coastal zone 30 to 40 m. wide and the low-lying states already mentioned, rise from sea-level to an elevation of 3280 ft. The tierra templada, or sub-tropical zone, rises to an elevation of 5577 ft., and comprises “the greater portions of Coahuila, Nuevo León, San Luis Potosi, nearly half of Tamaulipas, a small part of Vera Cruz, nearly the whole of Chiapas, nearly all of Oaxaca, a large portion of Guerrero, Jalisco, Sinaloa and Sonora,” together with small parts of the inland states of Puebla, Mexico, Morelos and Michoacan. The mean annual temperature is about 75°. Above this is the tierra fria, which ranges from 5577 to 8200 ft., and includes all the higher portions of the Mexican plateau, and which corresponds to the temperate regions of Central United States where frosts are very rarely experienced. Even here the high sun temperatures give a sub-tropical character to the country. In the sierras, above the tierras frias, which are not “cold lands” at all, are the colder climates of the temperate zone, suitable for cereals, grazing and forest industries, and, farther up, the isolated peaks which rise into the regions of snow and ice.

Speaking generally, the four seasons are clearly marked north of lat. 28° N. only. South of that parallel they merge in the estación de las aguas, or rainy season, from May to October, and the estación seca, or dry season, which prevails for the rest of the year. The rains generally begin on the east coast and gradually move northwards. The windward slopes of the Sierra Madre Oriental receive the greater part of the rainfall, and the winds, deprived of their moisture, pass over the northern plateau without further precipitation. On the Pacific coast the belt of calms, known as the northern horse latitudes, crosses the northern parts of Lower California and Sonora, which accounts for their extreme aridity. The southern terraces of the plateau have no high mountain barriers between them and the moist winds of the Caribbean, and they too receive an abundant rainfall in the wet season, especially during the prevalence of heavy “northers” on the Gulf coast. The precipitation varies widely, that of the western side of the northern plateau (Chihuahua and Durango) being about 39 in., that of the Valley of Mexico about 25 in., and that of the whole republic 59 in. Long droughts are common in many parts of the country, and on the barren surfaces of the plateau the rains drain away rapidly, leaving but slight beneficial results.

Flora and Fauna.—The types of animal and vegetable life found in Mexico belong, in a general sense, to those of the northern temperate region, and those of the tropical regions of Central and South America. The great central plateau and its bordering lowlands form an intermediate territory in which these dissimilar types are found side by side, the tropical species extending northward along the coast to the United States, while the northern species have found their way to the southern limits of the plateau. The jaguar and puma have found their way into the United States, while the wolf, coyote, bear and beaver have gone far southward on the plateau, and the buffalo was once found in large numbers on its more favoured northern plains. This intermingling of types does not apply to south-eastern Mexico, where animal life is represented by many of the genera and species found in the forested lowlands of the great, Amazon basin.,

Aside from its origin, the fauna of Mexico includes at least five species of monkey, the jaguar, puma, ocelot (Felis pardalis), wolf, coyote, lynx, badger, otter (Lutra felina), beaver, muskrat, bear, raccoon (Procyon), coati (Nasua), tapir, two species of peccary (Dicotyles torquatus and D. labiatus), skunk (Mephitis, Spilogale and Conepatus), marten, several species of opossum (including a pigmy species of the Tres Marias islands), sloth, two species of ant-bear (Myrmecophaga tetradactylus and Cyclothurus didactylus), armadillo (Dasypus novemcinctus), a small arboreal porcupine (Synetheres mexicanus), the kinkajou (Cercoleptes caudivolvulus), three species of deer—the white-tailed Cariacus toltecus, the little black-faced brocket, Coassus rufinus, which is also found in Brazil, and the Sonora deer (Odocoileus couesi)—the Mexican bighorn (Ovis mexicanus) of Chihuahua, at least two species of hare (Lepus calotis and L. palustris), rabbits, black, gray, red and ground squirrels, gophers, and many small rodents. Alligators and crocodiles are numerous in the lagoons and rivers of the coast and the iguana is to be found everywhere throughout the tropical lowlands, the large black Ctenosura acanthinurus being partly arboreal in habit when full grown; Mexico is a paradise of lizards, which are noted for their diversity in form as well as for their remarkable colouration. Frogs and toads are represented by scores of species, some of which, e.g. the tree-frogs (Hylidae), are extremely interesting. The ophidians are also very numerous, ranging from the comparatively harmless boa-constrictor to the deadly “palanca” or “fer de lance” (Lachesis lanceolatus) and rattlesnake (Crotalus), of which there are several species. In southern Mexico in 1902 and 1904 Hans Gadow collected specimens of 44 different kinds of snakes, which he estimated to be only about 45% of the species in the states visited. The arboreal life of the tropical forests has developed the tree-climbing habit among snakes as well as among frogs and toads, and also the habit of mimicry, their colour being in harmony with the foliage or bark of the trees which form their “hunting-grounds.” Bats are numerous, both in species and individuals. The sanguinary vampire (Desmodus rufus) has an extensive range through the tierras calientes and tierras templadas of the southern states. The coasts of Mexico, together with their accessible lagoons and rivers, afford innumerable breeding-places for turtles, which include the large green and tortoise-shell species. In some places the capture of the latter is the source of a considerable export trade in tortoise-shell. The coast of Lower California is a favourite resort for the fur-bearing seal, and pearl oysters find a congenial habitat in the south waters of the Gulf. There are some good fishing-grounds on the coasts, but fishing as an organized industry does not exist. The inland waters, with the exception of Lake Chapala, have comparatively few species, but the government has introduced carp, brook-trout and salmon-trout.

The avifauna of Mexico includes most of the species of the tropical and temperate regions of America—such as parrots (chiefly the yellow-headed Chrysalis), parakeets (Conurus canicula), macaws (Ara macao and A. militaris), toucans, trogons, herons, egrets, ibis, spoonbills, boat-bills (Cancroma), ducks, pelicans, cormorants, bitterns, stilts, sandpipers, curlews, grackles, kingfishers, motmots, “Chachalacas” (Ortalida poliocephala), woodpeckers, jays, cuckoos, “garrapateros” (Crotophaga sulcirostris), the ingenious weaver-bird (Icterus), and another species (Cassicus), whose curiously woven, sack-like nests are suspended from the slender limbs of trees, and sometimes even from telegraph-wires, scarlet-crested fly-catchers (Muscivora mexicana), tanagers, mocking-birds (called “zenzontl”), turkeys, partridge, quail (Colinus, Lophortyx, Callipepla and Cyrtonyx), doves, pigeons, eagles, caracara hawks (Polyborus), fish-hawks, falcons, crows, and turkey-buzzards (both the red-faced “aura” of North America and the black-faced “zopilote" of the tropics), which are the scavengers of the country. The most numerous, perhaps, are the humming-birds, of which there are many genera and species, each one distinct in form and colour. They are called “huitzilin” (spikelet by the Aztecs, and “colibrí,” “chupaflor” and “chupa-miel” (flower- or honey-sucker), and “pájaromosca” (fly-bird) by the Spanish-speaking Mexicans. These descriptive names are highly poetic, as also that of the Portuguese, “beija-flor” (flower-kisser); but the humming-bird is insectivorous, and thrusts his long bill into flowers in search of insects instead of honey. Mexico is credited with a great variety of song-birds, but these are to be found chiefly in the partly-forested country of the tierras templadas and tierras frias. Her chief distinction, however, is in birds of varied and gorgeous feathering. The wonderful plumage of the “quetzal” (Trogon resplendens) was, it is said, reserved