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Rh he obtained the girl in marriage, and his happy married life caused him ever afterwards to be invoked in marriage songs (Servius on Virgil, Aen. i. 651). According to another story, he was a youth who was killed by the fall of his house on his wedding day; hence he was invoked, to propitiate him and avert a similar fate from others (Servius, loc. cit.). He is represented in works of art as an effeminate-looking, winged youth, carrying a bridal torch and wearing a nuptial veil. The marriage song was sung, with musical accompaniment, during the procession of the bride from her parents’ house to that of the bridegroom, Hymenaeus being invoked at the end of each portion.

See R. Schmidt, De Hymenaeo el Talasio (1886), and J. A. Hild in Daremberg and Saglis’s Dictionnaire des antiquités.

HYMENOPTERA (Gr. , a membrane, and  , a wing), a term used in zoological classification for one of the most important orders of the class  (q.v.). The order was founded by Linnaeus (Systema Naturae, 1735), and is still recognized by all naturalists in the sense proposed by him, to include the saw-flies, gall-flies, ichneumon-flies and their allies, ants, wasps and bees. The relationship of the Hymenoptera to other orders of insects is discussed in the article , but it may be mentioned here that in structure the highest members of the order are remarkably specialized, and that in the perfection of their instincts they stand at the head of all insects and indeed of all invertebrate animals. About 30,000 species of Hymenoptera are now known.

Characters.—In all Hymenoptera the mandibles (fig. 1, C, D) are well developed, being adapted, as in the more lowly winged insects, such as the Orthoptera, for biting. The more generalized Hymenoptera have the second maxillae but slightly modified, their inner lobes being fused to form a ligula (fig. 1, B, b). In the higher families this structure becomes elongated (fig. 2, g) so as to form an elaborate sucking-organ or “tongue.” These insects are able, therefore, to bite as well as to suck, whereas most insects which have acquired the power of suction have lost that of biting. Both fore- and hind-wings are usually present, both pairs being membranous, the hind-wings small and not folded when at rest, each provided along the costa with a row of curved hooks which catch on to a fold along the dorsum of the adjacent fore-wing during flight. A large number of Hymenoptera are, however, entirely wingless—at least as regards one sex or form of the species. One of the most remarkable features is the close union of the foremost abdominal segment (fig. 3, i.) with the metathorax, of which it often seems to form a part, the apparent first abdominal segment being, in such case, really the second (fig. 3, ii.). The true first segment, which undergoes a more or less complete fusion with the thorax is known as the “median segment” or propodeum. In female Hymenoptera the typical insectan ovipositor with its three pairs of processes is well developed, and in the higher families this organ becomes functional as a sting (fig. 5),—used for offence and defence. As regards their life history, all Hymenoptera undergo a “complete” metamorphosis. The larva is soft-skinned (eruciform), being either a caterpillar (fig. 6, b) or a legless grub (fig. 7, a), and the pupa is free (fig. 7, c), i.e. with the appendages not fixed to the body, as is the case in the pupa of most moths.

Structure.—The head of a hymenopterous insect bears three simple eyes (ocelli) on the front and vertex in addition to the large compound eyes. The feelers are generally simple in type, rarely showing serrations or prominent appendages; but one or two basal segments are frequently differentiated to form an elongate “scape,” the remaining segments—carried at an elbowed angle to the scape—making up the “flagellum”; the segments of the flagellum often bear complex sensory organs. The general characters of the jaws have been mentioned above, and in detail there is great variation in these organs among the different families. The sucking tongue of the Hymenoptera has often been compared with the hypopharynx of other insects. According to D. Sharp, however, the hypopharynx is present in all Hymenoptera as a distinct structure at the base of the “tongue,” which must be regarded as representing the fused laciniae of the second maxillae. In the thorax the pronotum and prosternum are closely associated with the mesothorax, but the pleura of the prothorax are usually shifted far forwards, so that the fore-legs are inserted just behind the head. A pair of small plates—the tegulae—are very generally present at the bases of the fore-wings. The union of the first abdominal segment with the metathorax has been