swallow Any of 74 species (family Hirundinidae) of songbirds found nearly worldwide. Swallows are 4-9 in. (10-23 cm) long, with long, pointed, narrow wings; a short bill; small, weak feet; and sometimes a forked tail. The dark upper plumage may have a metallic blue or green sheen. Swallows capture insects on the wing. They nest in tree holes, burrow into sandbank, or plaster mud nests to walls. Some species (e.g., the common swallow, Hirundo rustica) are long-distance migrants; all have a strong homing instinct.
The swallows of California’s San Juan Capistrano Mission are cliff swallows ( Petrochelidon pyrrho- nota ). See also martin.
swallowing or deglutition
N.de-.glii-'tish-onV Act that moves food from the mouth to the stomach. The tongue pushes liquid or chewed food mixed with saliva into the pharynx. Reflex takes over as the soft pal¬ ate rises to close off the nasal cavity; the larynx rises and the epiglottis covers the trachea, interrupting breathing. Pressure in the mouth and phar¬ ynx pushes food toward the esophagus, whose upper sphincter opens to let food in and closes to prevent backflow. Breathing resumes as the lar-
Hirundimdae) of songbirds found
Common swallow (Hirundo rustica).
STEPHEN DALTON-NATURAL HISTORY PHOTOGRAPHIC AGENCY/EB INC.
© 2006 Encyclopaedia Britannica, Inc.
1852 I swallowtail butterfly ► Swaziland
ynx lowers. As peristalsis pushes food to the stomach, the lower esoph¬ ageal sphincter opens and then closes to prevent reflux. Painful swallowing is usually caused by inflammation; other problems are caused by blockage or disorders affecting the motions of swallowing.
swallowtail butterfly Any of more than 500 species (genus Papilio, family Papilionidae) of butterflies found worldwide except in the Arctic. Some have tail-like extensions of the hind wing. Colour patterns vary with species, sex, season, and sometimes location (see tiger swallowtail). Most adults have yellow, orange, red, green, or blue markings on an iridescent black, blue, or green background. The brightly coloured larvae eat foli¬ age. Some have markings resembling a snake’s head, and many discharge a bad-smelling substance when disturbed. The giant swallowtail (P. cre- sphontes ), with a wingspan of 4-5.5 in. (10-14 cm), is the largest but¬ terfly in the U.S. and Canada.
swami See sadhu and swami
Swammerdam Vsvam-or-.danA, Jan (b. Feb. 12, 1637, Amsterdam, Neth.—d. Feb. 15, 1680, Amsterdam) Dutch naturalist. An adept micros- copist, in 1658 he became the first person to observe and describe red blood cells. In his General History of Insects he accurately described and illustrated the life histories and anatomy of many insect species and clas¬ sified insects into four major divisions, three of which have been more or less retained in modern classification. He studied tadpole and adult frog anatomy and described the ovarian follicles of mammals. His improved techniques for injecting wax and dyes into cadavers had important con¬ sequences for the study of human anatomy. He showed that muscles alter in shape but not in size during contraction.
swamp Freshwater wetland ecosystem characterized by poorly drained mineral soils and plant life dominated by trees. Swamps have a sufficient water supply to keep the ground waterlogged, and the water has a high- enough mineral content to stimulate decay of organisms and to prevent the accumulation of organic materials. They are found throughout the world. See also marsh.
port; thereafter it grew steadily with industry, and by the mid-19th cen¬ tury it was the focus of the world copper trade. The city centre was almost totally destroyed by German bombing in 1941 but has been redeveloped, and Swansea is now the chief shopping and service hub for southwestern Wales. The poet Dylan Thomas was born there.
SWAPO See South West Africa People's Organization
Swarthmore College Private liberal arts college in Swarthmore, Pa., near Philadelphia. It was founded by a group of Quakers in 1864. Con¬ sistently ranked as one of the best colleges in the U.S., it offers bachelor’s degree programs in a wide variety of disciplines. It participates in an exchange program with Bryn Mawr and Haverford colleges and the Uni¬ versity of Pennsylvania.
swastika Equilateral cross with its arms bent at right angles, all in the same rotary direction, usually clockwise. It is used widely throughout the world as a symbol of prosperity and good fortune. In India, it continues to be the most common auspicious symbol of Hindus and Jains, as well as for Buddhists, for whom it symbolizes the Buddha’s feet or footprints. In China and Japan, where it traveled with the spread of Buddhism, it has been used to denote plurality, prosperity, and long life. It occurs as a motif in early Christian and Byzantine art, as well as in Maya and Navajo art. The counterclockwise swastika, suggested as a general anti-Semitic sym¬ bol in 1910 by the German poet and nationalist Guido von List, was adopted as the symbol of the Nazi Party at its founding in 1919-20.
Swazi Vswa-ze\ or Swati Vswa-te\ Bantu-speaking people inhabiting the grasslands of Swaziland and neighbouring regions of South Africa and Mozambique. With the Zulu and the Xhosa, the Swazi (numbering more than two million) form the southern Nguni ethnolinguistic group. They are chiefly agriculturalists and pastoralists. The highest traditional politi¬ cal, economic, and ritual powers are shared by a hereditary male ruler and his mother. The king’s wives and children are settled in royal villages, diplomatically dispersed throughout the territory.
Swaziland officially Kingdom of Swaziland Country, southern Africa. Area: 6,704 sq mi (17,364 sq km). Population (2005 est.): 1,032,000. Capitals: Mbabane (administrative and judicial), Lobamba (leg-
swan Long-necked, heavy-bodied, big-footed waterfowl (genus Cygnus,
family Anatidae). Among waterfowl, swans are the largest and fastest, both swimming and flying; at about 50 lbs (23 kg), the mute swan (C. olor ) is the heaviest flying bird. Swans dabble in shallows for aquatic plants. Five all-white, black-legged species live in the Northern Hemi¬ sphere; a black and a black-necked species live in the Southern Hemi¬ sphere. Males (cobs) and females (pens) look alike. Swans mate for life. The cob keeps guard while the pen incubates, on average, six eggs on a heap of vegetation; the young (cygnets) are tended for several months. Their graceful form when swimming has made swans emblems of beauty for centuries.
Mute swan (Cygnus olor) and cygnet
ARTHUR W. AMBLER-THE NATIONAL AUDUBON SOCIETY COLLECTION/PHOTO RESEARCHERS
Swan, Sir Joseph (Wilson) (b. Oct. 31, 1828, Sunderland, Durham, Eng.—d. May 27, 1914, Warlingham, Surrey) English physicist and chemist. By 1871 he had invented the dry photographic plate, an impor¬ tant improvement in photography. He had already produced an early elec¬ tric lightbulb (1860), and in 1880, independently of Thomas Alva Edison, he produced a carbon-filament incandescent electric lamp. He also pat¬ ented a process for squeezing nitrocellulose through holes to form fibres, a process that became widely employed in the textile industry.
Swan River Ephemeral river, southwestern Western Australia. It flows 224 mi (360 km) west to the Indian Ocean. Called the Avon in its upper course, it is known as the Swan only along its lower 60-mi course. Perth lies near its mouth. The river is dry during much of the summer and autumn. In 1829, western Australia’s first free settlement was made on its banks.
Swansea Vswan-ze\ Welsh Abertawe X.a-bor-'tau-oV Seaport and county (pop., 2001: 223,293), southern Wales. Lying along the Bristol Channel, it is the second largest city in Wales. It dates from the 12th cen¬ tury. Until the early 18th century it was a small market town and coal
islative), Lozitha and Ludzidzini (royal). Some four-fifths of the population is Swazi and about one-tenth is Zulu, with a small number of other minorities. Languages: Swazi (Swati), English (both official). Religions: Christianity (predominantly other [African, unaffiliated] Chris¬ tians; also Protestant, Roman Catholic); also traditional beliefs. Currency: lilangeni. The landlocked country is composed of high, middle, and low