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English colonies of North America is not known with certainty, but 

 it was well established in the settled parts by the beginning of the 

 eighteenth century. Soon after the arrival of the brown rat, the 

 black species began to decrease in numbers, and has become extinct 

 in most localities. At present it is not uncommon in some parts of 

 the South, and still occurs in scattered colonies in Canada and some 

 of the States east of the Mississippi, and also on some of the coastal 

 islands. It is occasional in many of our seaports, being apparently 

 brought from the Far East in merchandise. Except in a few ports 

 like San Francisco, where new arrivals are probably rather frequent, 

 these introduced individuals are often destroyed before they multiply. 

 The history of the black rat in Europe and its disappearance before 

 the brown rat is an exact parallel to its history here, and the animal 

 is now comparatively rare north of the Alps, except in the Channel 

 Islands. 



The Biological Survey has specimens of the black rat from Massa- 

 chusetts, New Hampshire, Georgia, Florida, Alabama, California, 

 and Washington, and also from Mexico, Honduras, Nicaragua, and 

 Hawaii. There are authentic records of its recent occurrence in 

 Newfoundland, Quebec, Nova Scotia, New York, North Carolina, 

 Tennessee, West Virginia, and Mississippi. In parts of South and 

 Middle America it is abundant. 



The roof or Alexandrian rat ( M. alexandrinus) is similar to the black 

 rat in form and general habits, though not in color. Little is known 

 of its history, but it is thought to be a native of Egypt, where it is 

 still abundant. It has established itself in many parts of the world, 

 mainly in warm climates, and is common near the coast in the 

 southern parts of the United States. 



The Biological Survey has specimens of the roof rat from North 

 Carolina, Georgia, Florida, Alabama, Mississippi, Texas, Arizona, 

 and California. In the last-named State it is abundant in the Sacra- 

 mento Valley. It is known also from Dismal Swamp, Virginia, and 

 from Cuba, the Bermudas, Trinidad, San Domingo, Costa Rica, 

 Nicaragua, Mexico, and Hawaii. Also, it inhabits many parts of 

 South America, where in places it is the dominant species. 



The most destructive of the rat family is the brown rat ( M. nor- 

 vegicus}. In most parts of the United States it is the common rat 

 about houses and barns in the country and about markets, wharves, 

 and warehouses in cities. It is larger and more robust than either 

 the black or the roof rat, and differs from both in habits. It is more 

 of a burrower, and lives in excavations which it makes under build- 

 ings and in loose soil along hedges and river banks. This habit, 

 combined with its greater strength and ferocity has enabled it to sup- 

 plant the other species in temperate latitudes; but in the warmer 

 parts of America and the Old World it has not been able to drive out 



