Online Encyclopedia

Search over 40,000 articles from the original, classic Encyclopedia Britannica, 11th Edition.

TERZ7

Online Encyclopedia
Originally appearing in Volume V13, Page 431 of the 1911 Encyclopedia Britannica.
» Make a correction to this article.
» Add information or comments to this article.
Spread the word: del.icio.us del.icio.us it!

TERZ7 .~ After See also:

Howard, Ent. See also:Bull. 4, n. s. (U.S. Dept. See also:Age). See also:boring See also:grub of a longhorn-See also:beetle or of the saw-See also:fly Sirex, with its stumpy vestiges of thoracic legs; the large-headed but entirely legless, fleshy grub of a See also:weevil; and the legless larva, with greatly reduced See also:head, of a See also:bee. The various larvae of the above See also:series, however, have all a distinct head-See also:capsule, which is altogether wanting in the degraded fly maggot. These See also:differences in larval See also:form denend in See also:part on the surroundings among which the larva finds itself after hatching; the active, armoured grub has to seek See also:food for itself and to fight its own battles, while the soft, defenceless maggot is provided with abundant nourishment. But in See also:general we find that elaboration of imaginal structure is assocated with degradation in the nature of the larva, eruciform and vermiform larvae being characteristic of the highest orders of the See also:Hexapoda, so that unlikeness between See also:parent and offspring has increased with the See also:evolution of the class. Hypermetamorphosis.—Among a few of the beetles or See also:Coleoptera (q.v.), and also in the neuropterous genus Mantispa, are found See also:life-histories in which the earliest instar is campodeiform and the succeeding larval stages cruciform. These later stages, comprising the greater part of the larval See also:history, are adapted for an inquiline or a parasitic life, where shelter is assured and food abundant, while the See also:short-lived, active See also:condition enables the newly-hatched See also:insect to make its way to the spot favourable for its future development, clinging, for example, in the See also:case of an oil-beetle's larva, to the hairs of a bee as she flies towards her See also:nest.

The presence of the two successive larval forms in the life-history constitutes what is called hyper-See also:

metamorphosis. Most significant is the See also:precedence of the eruciform by the campodeiform type. In See also:conjunction with the association mentioned above of the most highly See also:developed imaginal with the most degraded larval structure, it indicates clearly that the active, armoured grub preceded the sluggish soft-skinned See also:caterpillar or maggot in the evolution of the Hexapoda. Nymph.—The See also:term nymph is applied by many writers on the Hexapoda to all See also:young forms of See also:insects that are not sufficiently unlike their parents to be called larvae. Other writers apply the term to a " See also:free " pupa (see infra). It is in wellnigh universal use for those instars of ametabolous and hemimetabolous insects in which the See also:external wing-rudiments have become conspicuous (fig. 27). The mature See also:dragon-fly nymph, for example, makes its way out of the See also:water in which the See also:early stages have been passed and, clinging to some water-plant, undergoes .the final ecdysis that the imago may emerge into the See also:air. Like most ametabolic and hemimetabolic Hexapoda, such See also:nymphs continue to move and feed throughout their lives. But examples are not wanting of a more or less See also:complete resting See also:habit during the latest nymphal instar. In some cicads the mature nymph ceases to feed and remains quiescent within a See also:pillar-shaped earthen chamber. The nymph of a thrips-insect (See also:Thysanoptera) is sluggish, its legs and wings being sheathed by a delicate membrane, while the nymph of the male See also:scale-insect rests enclosed beneath a waxy covering.

Sub-imago.—Among the Hexapoda generally there is no subsequent ecdysis nor any further growth after the See also:

assumption of the winged See also:state. The may-flies, however, offer a remarkable exception to this See also:rule. After a prolonged aquatic larval and nymphal life-history, the winged insect appears as a sub-imago, whence, after the casting of a delicate cuticle, the true imago emerges. Pupa.—In the metabolic Hexapoda the resting pupal instar shows externally the wings and other characteristic imaginal See also:organs which have been gradually elaborated beneath the larval cuticle. It is usual to distinguish between the free pupae (fig. 26, b)—of Coleoptera and See also:Hymenoptera, for example —in which the wings, legs and other appendages are not fixed to the See also:trunk, and the obtect pupae (fig. 21, d)—such as may be noticed in the See also:majority of the See also:Lepidoptera—whose append- - ages are closely and immovably pressed to the See also:body by a general hardening and See also:fusion of the cuticle. In the degree of mobility there is See also:great diversity among pupae. A See also:gnat pupa swims through the water by powerful strokes of its See also:abdomen, while the caddis-fly pupa, in preparation for its final ecdysis, bites its way out of its subaqueous protective case and rises through the water, so that the fly may emerge into the air. Some pupae are thus more active than some nymphs; the essential See also:character of a pupa is not therefore its passivity, but that it is the instar in which the wings first become evident externally. The See also:division of the winged Hexapoda into Exopteryga and Endopteryga is thus again justified. If we admit that the larva has, in the phylogeny of insects, gradually diverged from the imago, and if we recollect that in the ontogeny the larva has always to become the imago (and of course still does so) notwithstanding the increased difficulty of the transformation, we cannot but recognize that a See also:period of helplessness in which the transformation may take See also:place is to be expected.

It is generally considered that this is sufficient as an explanation of the existence of the pupa. This, however, is not the case, because the greater part of the transformation precedes the disclosure of the pupa, which, as L. C. See also:

Miall remarks, is structurally little other " than the fly enclosed in a temporary skin." Moreover, in many insects with imperfect metamorphosis the See also:change from larva or (as the later See also:stage of the larva is called in these cases) nymph to imago is about as great as the corresponding change in the Holometabola, as the student will recognize if he recalls the histories of Ephemeridae, Odonata and male Coccidae. But in none of these latter cases have the wings to be changed from a position inside the body to become external and actively functional organs. The difference between the nymph or false pupa and the true pupa is that in the latter a whole stage is devoted to the perfecting of the wings and body-See also:wall after the wings have become external organs; the stage is one in which no food is or can be taken, however prolonged may be its existence. Amongst insects with imperfect metamorphosis the nearest approximations to the true pupa of the Holometabola are to be found in the subimago a Prom Chittenden, Bull. 4 (n.s.) See also:Dir. Ent. U.S. Dept. Arr.

of Ephemeridae and in the quiescent or resting stages of Thysanoptera, Aleurodidae and Coccidae. A much more thorough appreciation than we yet possess of the phenomena in these cases is necessary in See also:

order completely to demonstrate the tpecial characteristics of the holometabolous transformation. But even at See also:present we can correctly state that the true pupa is invariably connected with the transference of the wings from the interior to the exterior of the body. It cannot but suggest itself that this transference was induced by some peculiarity as to formation of cuticle, causing the growth of the wings to be directed inwards instead of outwards. We may remark that fleas possess no wings, but are understood to possess a true pupa. This is a most remarkable case, but unfortunately very little See also:information exists as to the details of metamorphosis in this See also:group. Life-Relations.—Only a brief reference can be made here co the fascinating subject of the life-relations of the larva, nymph and pupa, as compared with those of the imago. For details, the reader may consult the See also:special articles on the various orders and See also:groups of insects. A See also:common result of metamorphosis is that the larva and imago differ markedly in their See also:habitat and mode of feeding. The larva may be aquatic, or subterranean, or a burrower in See also:wood, while the imago is aerial. It may bite and devour solid food, while the imago sucks liquids. It may eat roots or refuse, while the imago lives on leaves and See also:flowers.

The aquatic habit of many larvae is associated with endless beautiful adaptations for respiration. The series of paired spiracles on most of the trunk-segments is well displayed, as a rule, in terrestrial larvae—caterpillars and the grubs of most beetles, for example. In many aquatic larvae we find that all the spiracles are closed up, or become functionless, except a pair at the hinder end which are associated with some arrangement—such as the valvular flaps of the gnat larva or the telescopic tail " of the See also:

drone-fly larva—for piercing the See also:surface film and See also:drawing periodical supplies of atmospheric air. A similar restriction of the functional spiracles to the tail-end(fig. 25, d) is seen in many larvae of flies (See also:Diptera) that live and feed buried in carrion or excrement. Other aquatic larvae have the tracheal See also:system entirely closed, and are able to breathe dissolved air by means of tubular or See also:leaf-like gills. Such are the grubs of See also:stone-flies, may-flies (fig. 27) and some dragon-flies and midges. An interesting feature is the difference often to be observed between an aquatic larva and pupa of the same insect in the See also:matter of breathing. The gnat larva, for example, breathes at the tail-end, See also:hanging head-downwards from the surface-film. But the pupa hangs from the surface .by means of paired See also:respiratory trumpets on the prothorax, the dorsal thoracic surface, where the cuticle splits to allow the emergence of the fly, being thus directed towards the upper air. A marked disproportion between the life-term of larva and imago is common; the former often lives for months or years, while the latter only survives for See also:weeks or days or See also:hours.

Generally the larval is the feeding, the imaginal the breeding, stage of the life-See also:

cycle. The extreme of this " division of labour " is seen in those insects whose jaws are vestigial in the winged state, when, the need for feeding all behind them, they have but to pair, to See also:lay eggs and to See also:die. The acquisition of wings is the sign of developed reproductive See also:power. Paedogenesis.—Nevertheless, the See also:function of See also:reproduction is occasionally exercised by larvae. In 1865 N. See also:Wagner made his classical observations on the See also:production of larvae from unfertilized eggs developed in the precociously-formed ovaries of a larval See also:gall-midge (Cecidomyid), and subsequent observers have confirmed his results by studies on insects of the same See also:family and of the related Chironomidae. The larvae produced by this remarkable method (paedogenesis) of virgin-reproduction are hatched within the parent larva, and in some cases See also:escape by the rupture of its body. Polyembryony.—Occasionally the power of reproduction is thrown still farther back in the life-history, and it is found that from a single See also:egg a large number of embryos may be formed. P. Marchal has (1904) described this power in two small parasitic Hymenoptera—a Chalcid (Encyrtus) which See also:lays eggs in the developing eggs of the small See also:moth Hyponomeuta, and a Proctotrypid (See also:Polygnotus) which infests a gall-midge (Cecidomyid) larva. In the egg of these insects a small number of nuclei are formed by the division of the See also:nucleus, and each of these nuclei originates by division the See also:cell-layers of a See also:separate embryo. Thus a See also:mass or See also:chain of embryos is produced, lying in a common cyst, and developing as their larval See also:host develops.

In this way over a See also:

hundred embryos may result from a single egg. Marchal points out the See also:analogy of this phenomenon to the artificial polyembryony that has been induced in Echinoderm and other eggs by separating the blastomeres, and suggests that the abundant food-See also:supply afforded by the host-larva is favourable for this multiplication of embryos, which may be, in the first instance, incited by the abnormal osmotic pressure on the egg. Duration of Life.—The See also:flour-moth (Ephesiia kuhniella) sometimes passes through five or six generations in a single See also:year. Although one of the characteristics of insects is the brevity of their adult lives, a considerable number of exceptions to the general rule have been discovered. These exceptions may be briefly summarized as follows: (1) Certain larvae, provided with food that may be adequate in quantity but deficient in nutriment, may live and go on feeding for many From Miall and Denny (after Vayssiere), The See also:Cock. See also:roach, See also:Lovell See also:Reeve & Co. at See also:Conjeeveram, and to the following See also:century some of the temples in the See also:south of the Bombay See also:Presidency, and the famous monolithic See also:temple of the See also:Kailas at See also:Ellora near See also:Aurangabad. Buildings in the See also:Dravidian See also:style are very numerous in proportion to the extent of the See also:area in which they are found. The temples generally consist of a square See also:base, ornamented externally by thin tall pilasters, and containing the cell in which the See also:image is kept. In front of this may be added a mantapam or See also:hall, or even two such. Over the See also:shrine rises the See also:spire, of pyramidal form, but always divided into storeys and crowned by a small See also:dome, either circular or polygonal in shape. The cornices are of See also:double curvature, whilst in other See also:Indian styles they are mostly straight with a downward slope. Another feature of these temples, especially those of later date, is the gopurams or great gateways, placed at the en-trances to the surrounding courts, and often on all four sides.

In general See also:

design they are like the See also:spires over the shrines, but about twice as wide as deep, and very frequently far more imposing than the temples them- selves. The style is distinctly of wooden origin, and of this the very attenuated pilasters on the See also:outer walls and the square pillars of small See also:section are evidences. As the specimen of the style: and at Avantipur, Vangath, Payer and Pandrethan are other interesting examples of the style. That at Pandrethan about 3 M. from See also:Srinagar is a well-preserved little temple, built between A.U. 906 and 921, and perhaps exhibits the most clearly the characteristics of the style. In the Himalayas the See also:architecture is still largely wooden, raised on stone basements and is often picturesque. In the See also:Nepal valley we meet with hemispherical chaityas or stupas on See also:low bases with lofty See also:brick spires, and some of them of great antiquity, along with temples having three or four storeys divided by sloping See also:roofs, and others in the See also:modern See also:Hindu style of See also:northern See also:India. In South See also:Kanara, especially at Mudbidare (Mudbidri), there are also Jain temples and tombs with double _ and triple sloping = roofs that resemble the -"' native temples of however, they had no connexion. The whole style is closely in See also:imitation of wooden originals, the forms of which have been derived from the See also:local thatched dwellings of the See also:district. The interiors of the Kanara temples are often very See also:rich in See also:carving, the massive pillars being carved like See also:ivory or the See also:precious metals. Associated with these and other temples are elegant, monolithic pillars placed on square bases, the shafts richly carved and the capitals wide-spreading, some of them supporting, on four very small colonnettes, a square roof elaborately modelled. These stambhas or pillars are the representatives of the early Buddhist lilts or columns raised at their temples, and See also:bear emblems distinctive of the sects to which they respectively belong.

The See also:

southern portion of the See also:peninsula is peopled by a See also:race known as Dravidians, and to the style of architecture practised over most of this area we may conveniently apply the name of the race. This Dravidian architecture was essentially different from that of other regions of India and is of one type. One of the best-known groups of monuments in this style is that of the " Seven Pagodas " or the Mamallapuram raths, on the seashore, south from See also:Madras. These raths are each hewn out of a See also:block of See also:granite, and are rather See also:models of temples than such. They are the earliest forms of Dravidian architecture and belong to the 7th century. To the same age belongs the temple of Kailasanath Scale iaa . contemporary northern styles are Reproducede , by permission of of n Mr dia See also:John See also:Murray, from Di characterized by Th See also:Cane Temples I y FIG. g.—See also:Plan of Kailas at Ellora. the prevalence of See also:vertical lines, the Dravidian is marked by See also:horizontal See also:mouldings and shadows, and the towers and gopurams are storeyed. The more. important temples are also surrounded by courts enclosing great corridors and pillared halls. One of the best examples of this style is the great temple at See also:Tanjore. It would appear to have been begun on a definite plan, and not as a series of extensions of some small temple which, by See also:accident, had grown famous and acquired See also:wealth by which successively to enlarge its courts, as that at Tiruvallur seems to have grown by a series of accretions. The body of the Tanjore temple is of two storeys and fully 8o ft. high, whilst the sikhara or pyramidal See also:tower rises in eleven storeys to a See also:total height of 190 ft.

This dominates the gopurams over the entrances to the See also:

court in which it stands, and to an outer court, added in front of the first, but which does not, as in other cases, surround it. The central shrine, so far as we know, was erected about A.D. 1025. The Srirangam temple in See also:Trichinopoly, the largest in India, is architecturally the converse of this: it is one of the latest in date, the fifth court having been See also:left unfinished in the See also:middle of the 18th century. The shrine is quite insignificant and distinguished only by a gilt dome, whilst proceeding outwards, the gopurams to each court are each larger and more decorative than the preceding. The successive See also:independent additions, however, proved incompatible with any considered design or arrangement of parts. Most of the See also:Deccan was ruled by the See also:Chalukya See also:dynasty from early in the 6th century, and the style prevailing over this area, Young resembling parents, but aquatic in habit, breathing dissolved air by thoracic tracheal gills. Includes the single family of the Perlidae (Stone-flies), formerly grouped with the See also:Neuroptera. Order : Isoptera. Biting mandibles; second maxillae incompletely fused. Fore-wings similar in shape and texture to See also:hind-wings, which do not See also:fold. In most See also:species the majority of individuals are wingless.

Short, jointed cerci. Six or eight Malpighian tubes. Young resembling adults; terrestrial throughout life. Includes two families, formerly reckoned among the Neuroptera —the Embiidae and Lise Termitidae or " See also:

White Ants ' (see See also:TERMITE). Order: Corrodentia. Biting mandibles; second maxillae incompletely fused; maxillulae often distinct. Cerci absent. Four Malpighian tubes. Includes two sub-orders, formerly regarded as Neuroptera: I. Copeognatha: Corrodentia with delicate cuticle. Wings usually developed ; the fore-wings much larger than the hind-wings. One family, the Psecidae (See also:Book-lice).

These See also:

minute insects are found amongst old books and See also:furniture. 2. Mallophaga: Parasitic wingless Corrodentia (See also:Bird-lice). Order: Ephemeroptera. Jaws vestigial. Fore-wings much larger than hind-wings. Elongate, jointed cerci. Genital ducts paired and entirely mesodermal. Malpighian tubes numerous (40). Aquatic larvae with distinct maxillulae, breathing dissolved air by abdominal tracheal gills. Penultimate instar a flying sub-imago. [Includes the single family of the Ephemeridae or may-flies.

See also NEUROPTERA, in which this order was formerly comprised.] Order : Odonata. Biting mandibles. Wings of both pairs closely alike; See also:

firm and glassy in texture. Prominent, unjointed cerci, male with genital See also:armature on second abdominal segment. Malpighian tubes numerous (50-6o). Aquatic larvae with caudal leaf-gills or with rectal tracheal system. Includes the three families of dragon-flies. Formerly comprised among the Neuroptera. Order: Thysanoptera. Piercing mandibles, retracted within the head-capsule. First maxillae also modified as piercers; maxillae of both pairs with distinct palps. Both pairs of wings similar, narrow and fringed.

Four Malpighian tubes. Cerci absent. Ovipositor usually present. Young resembling parents, but penultimate instar passive and enclosed in a filmy pellicle. Includes three families of Thrips (see THYSANOPTERA). Order: See also:

Hemiptera. Mandibles and first maxillae modified as piercers; second maxillae fused to form a jointed, grooved rostrum. Wings usually present. Four Malpighian tubes. Cerci absent. Ovipositor developed. Includes two sub-orders: I.

Heteroptera: Rostrum not in contact with haunches of fore-legs. Fore-wings partly coriaceous. Young resembling adults. Includes the bugs, terrestrial and aquatic. 2. Homoptera: Rostrum in contact with haunches of fore-legs. Fore-wings See also:

uniform in texture. Young often larvae. Penultimate instar passive in some cases. Includes the cicads, See also:aphides and scale-insects (see HEMIPTERA). Order: Anoplura. Piercing jaws modified and reduced, a tubular, protrusible sucking-trunk being developed; mouth with hooks.

Wingless, parasitic forms. Cerci absent. Four Malpighian tubes. Young resembling adults. Includes the family of the Lice (Pediculidae), often reckoned as Hemiptera (q.v.). See also See also:

LOUSE. Sub-class: ENDOPTERYGOTA. Hexapoda mostly with wings; the wingless forms clearly degraded or modified. Maxillulae vestigial or absent. No locomotor abdominal appendages (except in certain larvae). Young animals always unlike parents, the wing-rudiments developing beneath the larval cuticle and only appearing in a penultimate pupal instar, which takes no food and is usually passive. Order: Neuroptera.

Biting mandibles; second maxillae completely fused. Prothorax large and free. Membranous, See also:

net-veined wings, those of the two pairs closely alike. Six or eight Malpighian tubes. Cerci absent. Larva campodeiform, usually feeding by suction (exceptionally hypermetamorphic with subsequent eruciform instars). Pupa free. Includes the See also:alder-flies, See also:ant-lions and lacewing-flies.

End of Article: TERZ7

Additional information and Comments

There are no comments yet for this article.
» Add information or comments to this article.
Please link directly to this article:
Highlight the code below, right click, and select "copy." Then paste it into your website, email, or other HTML.
Site content, images, and layout Copyright © 2006 - Net Industries, worldwide.
Do not copy, download, transfer, or otherwise replicate the site content in whole or in part.

Links to articles and home page are always encouraged.

[back]
TERVUEREN 		[next]
TERZA RIMA

Site © 2006 - Net Industries