MIGRATION OF ANIMALS 



MIGUEL 



187 



or were, due to a scarcity of water and naturally 

 of food also. The occasional inroads of bears and 

 wolves on settled districts are not migrations 

 proper, for their boldness is stimulated solely by 

 hunger through the scarcity of food during more 

 than usually severe winters ; and to an allied cause 

 may be traced the long excursions of various 

 monkeys (Entellus and Rhesus) at irregular 

 periods. 



Many fishes are regular migrants. The salmon, 

 the shad, some smelts (the North-west American 

 oolachan, Otmeru* pacijicus, for example), eels, the 

 sea lamprey, the sturgeon, the river trout, &c., all 

 migrate from the sea up rivers at the spawning 

 season, while the roach and the ide of Scandinavia 

 migrate from lakes into the tributary streams for 

 the purpose of depositing their ova. The herring, 

 sprat, pilchard, and other Clupeidre move from 

 deep water in spring to shallower places more in- 

 shore, in order that the greater warmth of the 

 water may hatch the spawn ; while other species 

 (e.g. the sudden arrival of the Temnoilon saltator 

 off the southern coast of Morocco in 1887, and 

 succeeding seasons, after an absence for twenty- 

 seven years) appear and disappear periodically, 

 though in all probability most hshes are more or 

 less migratory. 



Among reptiles, turtles are the only known 

 migrants, moving on shore at fixed periods to 

 deposit their eggs in the sand, and disporting 

 themselves in the sea during the rest of the year. 



Among Invertebrate there are no regular migrants ; 

 but many of them (lerform irregular migrations of 

 considerable interest. The destructive flights of 

 various species of the Locust (q. v. ) and Grasshopper 

 (q. v. ) in search of green food, the occasional Nights 

 of butterflies, and the quasi-marches of the ter- 

 mites ants are cases in point. In July 1890, near 

 Komershof, in the Kiga district, there was wit- 

 in".->ed a flight of small lieetles. The mass in 

 motion was altont 2 miles long, 1J mile broad, and 

 7 yards thick. It moved in a northerly direction, 

 obscuring the sun, and at times settling on the 

 fields. The flights of the various species of locust 

 (especially Pachyti/lng miyratoriiis) are, how- 

 ever, not always impelled by hunger, for though 

 they generally breed in a "sandy district when 

 food is scarce, and are therefore compiled to 

 seek another where it is more plentiful, the 

 reverse course is sometimes taken, as if the 

 species was seeking the barren home of its 

 ancestors. Temperature may also have something 

 to do with locustal migrations, and there is a 

 tendency for the flights to take particular direc- 

 tions. The nearest approach to periodical migra- 

 tion known is the curious movement of butterflies 

 across the Isthmus of Panama and seaward in June 

 and the beginning of July many years in succession. 

 Hut it is not known where they go to, though butter- 

 fly showers have been met with in the Pacific 

 several miles from land, and other flights have 

 crowed Ceylon of such an extent that, though miles 

 in breadth, they occupied several continuous days 

 in their passage. It may lie taken for granted that 

 all marine animals, like all terrestrial ones, shift 

 about in search of food, when not permanently 

 fixed in their adult condition. Yet, with the ex- 

 ceptions mentioned, it is difficult to point to any 

 which are migrants in the true sense of the term. 

 A curious inroad of crustaceans a species of 

 Sesarma has l!en noticed oil' Cuba, where, at 

 Cape San Antonio, they invaded the houses and 

 the light-tower. Land-cralis are sometimes migra- 

 tory. The violet species of the West Indies ( Gecar- 

 cinia ruricola) lives several miles inland, returning 

 to the sea once a year to deposit its spawn. Other 

 species are found at heights of 4500 feet, in the 

 Deccan, though they do not appear to visit the sea, 



being fresh-water spawners. But in Ascension land- 

 crabs climb up Green Mountain and steal rabbits 

 from their boles, and in Japan the crab Teljihusa 

 is found on the tops of mountains several thousand 

 feet high, and in Greece and Italy by streams far 

 inland. 



Migration is, therefore, in the vast majority of 

 cases, due ( 1 ) to the necessity of secirching for food 

 and (2), as in the case of fishes, Crustacea, reptiles, 

 &c., of finding a suitable place for depositing their 

 eggs. The causes which impel birds to migrate 

 are more complicated, though the two mentioned 

 are the leading ones. With mammals, in all like- 

 lihood, this trait is of an origin so remote that it 

 preceded the present distribution of land and 

 water. This is shown by the range of various 

 extinct groups. Thus, true horses of the genus 

 Equus are of older-Pliocene date in Europe, but 

 of Post-Pliocene, or even of later appearance, in 

 America, into which they have migrated, though 

 on that continent they expired comparatively soon. 

 But tapirs, though now essentially an American 

 group, Win" more abundant there than in Asia, 

 are in the Old World Lower Miocene, while in the 

 New World they do not extend further back than 

 the Post- Pliocene epoch. Lastly and the list might 

 be largelyextended camelida?, though now confined 

 to Asia and South America, are really an American 

 group, having been largely developed in the Mio- 

 cene age of the northern part of the continent, 

 whereas the true camels, according to Wallace, seem 

 to have passed into Asia and the llamas into South 

 America. We may, indeed, infer with confidence 

 that in the most remote periods of the world's 

 history migration existed ; indeed, if we accept 

 (though few palaeontologists do) the conclusions of 

 Barrande, they lend countenance to the belief that 

 at a date incalculably distant by our methods of 

 measuring time this animal trait was established 

 among the trilobites and other palaeozoic inverte- 

 brates. It is thus, in some instances, permissible 

 to suggest that the habit is a 'survival, though it 

 is difficult to point to a case in which it is at 

 present practised without the animal benefiting 

 thereby. For just as hibernation, by enabling an 

 animal to live within its area, serves an important 

 purpose in the struggle for existence, so migration, 

 by enabling it to escape vicissitudes of climate and 

 the revolutions of the globe which would be fatal 

 to it or to its offspring, renders the species more 

 likely to survive longer than it would otherwise be 

 capable of doing. 



See De Serres, Da Causes do Migrations des Animaux 

 (1842); Brown, Short Studio from Nature, and Our 

 Earth; Palmen, Om Foijlarnes fli/ttninysrdyar (1874), 

 with liibliography of subject so far as birds are con- 

 cerned ; Harting, Our Summer Af tyrants (1877); Duns, 

 Science for All; Reports of the British Association 

 Committee on the Mil/ration of Birds ( 1883 gcqq. } ; 

 Richardson, fauna Boreftli-Amtricana ; Von Wrangel, 

 Jis/inlilion to the Polar Sta ; Eschricht, Forhand. Stan- 

 dinatiske Naturhittm-itke f'orenintj (1847); Kink, 

 Danish Greenland (1876); C. Dixon, The Migration of 

 British Birds (1892 and 1895) ; Gatke, Heligoland ai an 

 Ornithological Observatory ( 1895 ) ; Von Hiring, in Kosmos 

 (1883) ; Challenger Report, vol. i. p. 927 ; Nicholson and 

 Lydekker, Manual of Palaontology (1889); and the 

 article GEOGRAPHICAL DISTRIBUTION. 



Miguel, MARIA EVARIST, usurper of the throne 

 of Portugal, was born at Lisbon, 26th October 1802, 

 the third son of King John VI. A determined 

 hater of all constitutional principles, he plotted 

 (1824) to overthrow the constitutional form of 

 government granted by his father : he caused the 

 ministers to be arrested and his father to be closely 

 watched in his palace ; but the aged king escaped 

 to an English man-of-war anchored in the estuary. 

 Miguel and his mother, his principal abettor, were 

 banished. At the death of John VI. in 1826, the 



