called from its fanciful likeness to a snake. Numerous myths, in various countries, are however connected with it. The general character of these may be illustrated by the Greek story which explains the constellation as being the dragon of the Hesperides slain by Heracles and translated by Hera or Zeus to the heavens.
See C. V. Daremberg and E. Saglio, Dictionnaire des antiquités grecques et romaines (Paris, 1886, &c.), s.v. “Draco”; Pauly-Wissowa, Realencyclopädie, s.v. “Drakon”; Du Cange, Glossarium, s.v. “Draco”; La Grande Encyclopédie s.v. “Dragon”; J. B. Panthot, Histoire des dragons et des escarboucles (Lyons, 1691). See also the articles Egypt: Religion, and Babylonian and Assyrian Religion. (W. A. P.)
In zoology the name “dragon” is now applied to a highly interesting, but very harmless, group of small flying lizards forming the genus Draco, belonging to the Agamidae, a family of Saurian reptiles. About 20 species of “flying dragons” inhabit the various Indo-Malayan countries; one, D. dussumieri, occurs in Madras. They are small creatures, measuring about 10 in. long, including the tail, which in some cases is more than half of the entire length. The head is small, and the throat is provided with three pouches which are spread out when they lie on the trunks of trees. They are, however, chiefly remarkable for the wing-like cutaneous processes with which their sides are provided, and which are extended and supported by greatly elongated ribs. These form a sort of parachute by which the animals are enabled to glide from branch to branch of the trees on which they live, but, being altogether independent of the fore limbs, they cannot be regarded as true wings, nor do they enable the lizard to fly, but merely to make extensive leaps. But they have the habit of opening and folding these prettily coloured organs, when resting upon a branch, which gives them the appearance of butterflies. When not in use they are folded by the side after the manner of a fan, and the dragon can then walk or run with considerable agility. Its food consists of insects.
DRAGONETTI, DOMENICO (1763–1846), Italian double-bass player, was born in Venice on the 7th of April 1763. Having become famous as a performer on his instrument, he went to London in 1794, where his playing created a furore. He was the friend of Haydn and of Beethoven, and a well-known character in his day. He died in London on the 16th of April 1846.
DRAGON-FLY (Ger. Wasserjungfer; Swed. trollslända; Dan. guldsmed; Dutch, scherpstekendevlieg; Fr. demoiselle), the popular English name applied to the members of a remarkable group of insects which formed the genus Libellula of Linnaeus and the ancient authors. In some parts of the United States they appear to be known as “devil’s darning needles,” and in many parts of England are termed “horse-stingers.” It is almost needless to say that (excepting to other insects upon which they prey) they are perfectly innocuous, though some of the larger species can inflict a momentarily painful bite with their powerful jaws. Their true systematic position is still contested and somewhat uncertain. By most of the older systematists they were placed as forming part of the heterogeneous order Neuroptera. J. C. Fabricius, however, elevated them to the rank of a distinct order, which he termed Odonata; and whatever may be the difference of opinion amongst authors at the present day, that term is almost universally employed for the group. W. F. Erichson transferred all the groups of so-called Neuroptera with incomplete metamorphoses, hence including the dragon-flies, as a division of Orthoptera, which he termed Pseudo-Neuroptera. K. E. A. Gerstäcker more recently also retains them in the Orthoptera, terming those groups in which the earlier states are subaquatic Orthoptera amphibotica. All entomologists are agreed in maintaining the insects as forming a group marked by characters at once extraordinary and isolated in their nature, and in most modern classifications they are treated as a distinct order.
The group Odonata is divided into three families, and each of these again into two subfamilies. The families are the Agrionidae, Aeschnidae and Libellulidae—the first including the subfamilies Calopterygina and Agrionina, the second Gomphina and Aeschnina, and the third Cordulina and Libellulina.
Anatomy.—The structure of a dragon-fly being so very remarkable, it is necessary to enter somewhat extensively into details. The head is comparatively small, and excavated posteriorly, connected very slightly with the prothorax, on which it turns almost as on a pivot. The eyes are, as a rule, enormous, often contiguous, and occupying nearly the whole of the upper surface of the head, but sometimes (Agrionidae and Gomphina) widely distant; occupied by innumerable facets, which are often larger on the upper portion. The antennae, which are smaller in proportion than in almost any other insects, consist only of two short swollen basal joints and a 5 or 6-jointed bristle-like thread. The large labrum conceals the jaws and inner mouth parts. The lower lip, or labium (formed by the conjoined second maxillae), is attached to a very small chin piece (or mentum), and is generally very large, often (Agrionidae) divided almost to its base into two portions, or more frequently entire or nearly so; on each side of it are two usually enormous hypertrophied pieces, which form the “palpi,” and which are often furnished at the tips with an articulated spine (or terminal joint), the whole structure serving to retain the prey. Considerable diversity of opinion exists with respect to the composition of the mouth parts, and by some authors the “palpi” have been termed the side pieces of the lower lip. The prothorax is extremely small, consisting of only a narrow ring. The rest of the thorax is very large, and consolidated into a single piece with oblique sutures on the sides beneath the wings.
The abdomen varies excessively in form, the two extremes being the filiform structure observable in most Agrionidae, and the very broad and depressed formation seen in the familiar British Libellula depressa. It consists of ten distinct segments, whereof the basal two and those at the apex are short, the others elongate, the first being excessively short. In a slit on the under side of the second in the male, accompanied by external protuberances, are concealed the genital organs: on the under side of the eighth in the female is a scale-like formation, indicating the entrance to the oviduct. The tenth is always provided in both sexes with prominent appendages, differing greatly in form, and often furnishing the best specific (and even generic) characters.
The legs vary in length and stoutness, but may, as a rule, be termed long and slender. The anterior pair probably assist in capturing and holding insect prey, but the greatest service all the legs render is possibly in enabling the creature to rest lightly, so that it can quit a position of repose in chase of passing prey in the quickest possible manner. The coxa is short and stout, followed by a still shorter trochanter; the femora and tibiae long and slender, almost invariably furnished on their under surface with two series of strong spines, as also are the tarsi, which consist of three slender joints, the last having two long and slender claws.
The wings are always elongate, and furnished with strong longitudinal neuration and dense transverse nervules strengthening the already strong (although typically transparent) membrane. In the Agrionidae both pairs are nearly equal, and are carried vertically and longitudinally in repose, and the neuration and membrane are less strong; hence the species of this family are not so powerful on the wing as are those of the other groups in which the wings are horizontally extended in a position ready for instant service. The neuration is peculiar, and in many respects without precise analogy in other groups of insects, but it is not necessary here to enter into more than some special points. The arrangement of the nervures at the base of the wing is very singular, and slight differences in it form useful aids to classification. In the Aeschnidae and Libellulidae this arrangement results in the formation of a triangular space (known as the “triangle”), which is either open or traversed by nervules; but in many Agrionidae this space, instead of being triangular, is oblong or elongately quadrate, or with its upper edge partly straight and partly oblique. This fixitude of type in neuration is not one of the least important of the many peculiarities exhibited in these insects.
The internal structure is comparatively simple. The existence of salivary glands, denied by L. Duprix, has been asserted by O. Poletajewa. The rest of the digestive apparatus consists of an elongate canal extending from mouth to anus, comprising the oesophagus, stomach and intestine, with certain dilatations and constrictions; the characteristic Malpighian vessels are stated to number about forty, placed round the posterior extremity of the stomach. Dragon-flies eat their prey completely, and do not content themselves by merely sucking its juices; the harder portions are rejected as elongate, nearly dry, pellets of excrement.
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| Fig. 1—The anterior portion of the body of Aeschna cyanea freed from the nymph-cuticle. | Fig. 2.—The tail being extricated. |
Pairing.—But the most extraordinary feature in the economy—one which has attracted the attention of naturalists from remote times—is the position of the genital organs, and the corresponding anomalous manner in which the pairing of the sexes and impregnation is effected. In the male the intromittent organ is situated in a slit on the under surface of the second abdominal segment; it is usually very crooked or sinuous in form, and is accompanied by sheaths, and by external hooks or secondary appendages, and also by seminal vessels. But the ducts of the vessels connected with the testes unite and open on the under surface of the ninth segment; hence, before copulation can take place, it is necessary that the vessels in the second
