Online Encyclopedia

ORTHOPTERA (Gr. Op®os, straight, and ...

Online Encyclopedia
Originally appearing in Volume V20, Page 341 of the 1911 Encyclopedia Britannica.
Spread the word: del.icio.us del.icio.us it!
ORTHOPTERA (Gr. Op®os, straight, and rTepov, a wing), a term used in zoological classification for a large and important order of the class Hexapoda. The cockroaches, grasshoppers, crickets and other insects that are included in this order were first placed by C. Linne (1735) among the Coleoptera (beetles), and were later removed by him to the Hemiptera (bugs, &c.). J. C. Fabricius (1775) was the first to recognize the unnaturalness of these arrangements, and founded for the reception of the group an order Ulonata. In 18o6 C. de Geer applied to these insects the name Dermaptera (SEpµa, a skin, and srrepov) ; and A. G. Olivier subsequently used for the assemblage the name Orthoptera, which is now much better known than the earlier terms. W. Kirby (1815) founded an order Dermaptera for the earwigs, which had formed part of de Geer's Dermaptera, accepting Olivier's term Orthoptera for the rest of the assemblage, and as modern research has shown that the earwigs undoubtedly deserve original separation from the cockroaches, grasshoppers, crickets, &c., this terminology will probably become established. W. E. Erichson and other writers added to the Orthoptera a number of families which Linne had included in his order Neuroptera. These families are described and their affinities discussed in the articles NEUROPTERA and HEXAPODA (qq.v.). In the present article a short account of the characters of the Dermaptera and Orthoptera is given, while for details the reader is referred to special articles on the more interesting families or groups. The Dermaptera and the Orthoptera agree in having well-developed mandibles, so that the jaws are adapted for biting ; in the incomplete fusion of the second maxillae (which form the labium) so that the parts of a typical maxilla can be easily made out (see the description and figures of the cockroach's jaws under HExAroDA); in the presence of a large number of excretory (Malpighian), tubes; in the firm texture of the forewings; in the presence of appendages (cerci) on the tenth abdominal segment; and in the absence of a metamorphosis, the young insect after hatching closely resembling the parent. Order Dermaptera. In addition to the characters just enumerated, the Dermaptera are distinguished by the presence of small but distinct maxillulae (fig. 2, see HEXAPODA, APTERA) in association with the tongue (hypopharynx) ; by the forewings when present being modified into short quadrangular elytra without nervuration, the complex hind-wings (fig. i) being folded beneath these both longitudinally and transversely so that nearly the whole abdomen is left uncovered; and by the entirely mesodermal nature of the genital ducts, which, according to the observations of F. Meinert, open to the exterior by a median aperture, the terminal part of the duct being single, either by the fusion of the primitive paired ducts or by the suppression of one of them. In the vast majority of winged insects the terminal part of the genital system (vagina and ductus ejaculatorius) is unpaired and ectodermal. Thus the condition in the Dermaptera is more primitive than in any other Pterygote order except the Ephemeroptera (Mayflies) which are still more generalized, the primitive mesodermal ducts (oviducts and vasa deferentia) opening by paired apertures as in the Crustacea. In the vast majority of the Dermaptera the cerci are—in the adult insect at least—stout, unjointed appendages forming a strong forceps (fig. 1) which the insect uses in arranging the hindwings beneath the elytra. In at least one genus the unjointed pincers of the forceps are preceded, in the youngest instar by jointed cerci. Very many members of the order are entirely wingless. There are two families of Dermaptera. The Hemimeridae include the single genus Hemimerus (q.v.), which contains only two species of curious wingless insects with long, jointed cerci, found among the hair of certain West African rodents. The other family is that of the Forficulidae or earwigs (q.v.), all of which have the cerci modified as a forceps, while wings of the characteristic form described above are present in many of the species. Order Orthoptera. The bulk of de Geer's " Dermaptera " form the order Orthoptera of modern systematists, which includes some lo,000 described species. The insects comprised in it are distinguished from the earwigs by their elongate, rather narrow forewings, which usually cover, or nearly cover, the abdomen when at rest, and which are firmer in texture than the hindwings. The hindwings have a firm costal area, and a more delicate anal area which folds fanwise,so that they are completely covered by the forewings when the insect rests. Rarely (in certain cockroaches) the hindwing undergoes transverse folding also. Wingless forms are fairly frequent in the order, but their relationship to the allied winged species is evident. The female of the common cockroach (fig. 3a) shows an interesting vestigial condition of the wings, which are but poorly developed in the male (fig. 3b). More important characters of the Orthoptera than the nature of the wings—characters in which they differ from After Marlatt, Ent. Bull. 4, n. s. U.S. Dept. Agr. the Dermaptera and agree with the vast majority of winged insects—are the absence of distinct maxillulae and the presence of an unpaired ectodermal tube as the terminal region of the genital system in both sexes. The cerci are nearly always joined, and a typical insectan ovipositor with its three pairs of processes is present in connexion with the vagina of the female. In many Orthoptera this ovipositor is very long and conspicuous (fig. 5). Information as to the internal structure of a typical orthopteron—the cockroach—will be found under HEXAPODA. Classification.—Six families of Orthoptera are here recognized, but most special students of the order consider that these should be rather regarded as super-families, and the number of families greatly multiplied. Those who wish to follow out the classification in detail should refer to some of the recent monographs mentioned below in the bibliography. There is general agreement as to the division of the Orthoptera into three sub-orders or tribes. I. Phasmidea.—This division includes the single family of the Phasmidae whose members, generally known as " stick-insects " (q.v.) and " leaf-insects " (q.v.), are among the best-known examples of "protective resemblance " to be found in the whole animal kingdom. The prothorax is short and the mesothorax very long, the three pairs of legs closely similar, the wings often highly modified or absent, and the cerci short and unjointed. Each egg is contained in a separate, curiously formed, seed-like capsule, provided with a lid which is raised to allow the escape of the newly-hatched insect. II. Oothecaria.—In this tribe are included Orthoptera with a large prothorax, whose eggs are enclosed in a common purse or capsule formed by the hardening of a maternal secretion. The Mantidae or " praying insects " have the prothorax elongate and the fore-legs powerful and raptorial, while the large, broad head is prominent. The eggs are enclosed in a case attached to a twig or stone and containing many chambers. From this curious habitation the young mantids hang by threads till after their first moult (see After Howard, Ent. Bull. 4, n. s. U.S. Dept. Agr. MANTIS). The Blattidae FIG. 4.—Egg-purse of American Cock-(fig. 3) or cockroaches roach (Periplaneta americana). Magnified. (q.v.) form the second a, Side view; b, end view; the outline family of this division. c shows natural size. They are readily dis- tinguished by the somewhat rounded prothorax beneath which the head is usually concealed, while the forelegs are unmodified. Sixteen eggs are enclosed together in a compact capsule or " purse " (fig 4)• From Carpenter's Insects. Dent & Co. C stridulating organs which produce chirping notes (see CRICKET). The families are the Acridiidae and Locustidae—including the insects familiarly known as locusts and grasshoppers (q.v.) and the Gryllidae or crickets (q.v.). The Acridiidae have the feelers and the ovipositor relatively short, and possess only three tarsal segments; their ears are situated on the first abdominal segment and the males stridulate by scraping rows of pegs on the inner aspect of the hind thigh, over the sharp edges of the forewing nervures. The Locustidae (see GRASSHOPPER, KATYDID) have the feelers and often also the ovipositor very elongate; the foot is four-segmented; the ears are placed at the base of the foreshin and the stridulation is due to the friction of a transverse " file " beneath the base of the left forewing over a sharp ridge on the upper aspect of the right. In some of these insects the wings are so small as to be useless for flight, being modified altogether for stridulation. The Gryllidae (fig. 5) are nearly related to the Locustidae, having long feelers and ovipositors, and agreeing with the latter family in the position of the ears. The forewings are curiously arranged when at rest, the anal region of the wing lying dorsal to the insect and the rest of the wing being turned downwards at the sides (see CRICKET). Fossil History.—The Orthoptera are an exceedingly interesting order of insects as regards their past history. In Palaeozoic rocks of Carboniferous age the researches of S. H. Scudder have revealed insects with the general aspect of cockroaches and phasmids, but with the two pairs of wings similar to each other in texture and form. In the Mesozoic rocks (Trias and Lias) there have been discovered remains of insects intermediate between those ancient forms and our modern cockroaches, the differentiation between forewings and hindwings having begun. The Orthopteroid type of wings appears therefore to have arisen from a primitive Isopteroid condition.
End of Article: ORTHOPTERA (Gr. Op®os, straight, and rTepov, a wing)
[back]
ORTHONYX
[next]
ORTHORHOMBIC SERIES

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." Paste it into a website, email, or other HTML document.