Page:The American Cyclopædia (1879) Volume VI.djvu/138

 130 DIPTERA DIPTYCHS genus stratiomys (Geoff.) has a broad oval body, of a dark color, with yellow markings on each Bide, and the antennae somewhat spindle-shaped. The genus sargus (Fabr.) is* said to have no spines on the thorax, a slender body, of a bril- liant grass-green, about half an inch long, with a bristle on the end of the antennae. These in- sects delight in sunny weather, being dull and inactive in cloudy days ; the larvae are found in dung and rich mould. The syrphidce have also a fleshy proboscis, and live on the honey of flowers ; they resemble bees, wasps, and hor- nets in shape and color, and sometimes lay their eggs in the nests of these insects ; others drop their ova among plant lice, which the young eagerly feed upon. The larvae of the genus helophilus (Meig.) were named by R6au- mur rat-tailed maggots, from the great length of their tubular tails, which serve as respi- ratory organs; the experiments of Reaumur show that while the insect lies concealed in mud, its respiratory tube may reach five inches to the surface of the water ; it seems to be composed of two portions, which slide one into the other like the joints of a telescope. Some of the larvae of this family live in rotten wood. The family conopidce resemble slender- bodied wasps ; the antennae are long and three- jointed ; the proboscis is long, slender,' and ge- niculate. The genus conops (Linn.) is generally black, and about half an inch long; more than 20 species are described, usually found on flow- ers in June and July, but not in large num- bers; they deposit their eggs in the larvae and the perfect insects of the bumblebee, in whose bodies their young undergo metamorphosis. The common stable fly belongs to the genus stomoxys (Fabr.); the flesh fly to sarcophaga (Meig.) ; the house fly and the meat fly to mmca (Linn.) ; the flower flies to anihomyia (Mi-ig.); the cheese fly to piopJiila (Fallen.) ; the dung fly to scatophaga (Meig.) ; the fruit and gall flies to ortalis (Fallen.) and tepJiritis (Latr.). (See FLY.) The gadflies or hot flies, comprising the genera oestrus (Linn.) and gas- terophilus (Leach), affect respectively the ox and the horse. (See GADFLY.) Various winged and wingless ticks infest the horse, sheep, and birds, belonging to the order of diptera, but forming with the spider flies the order homa- lopttra of Leach and the English entomologists; they include the genera hippolosca (Linn.), melophftgus (Latr.), and ornithomyia (Latr.). (See TICK.) The pttlicida, or fleas, are wing- less diptera, with hard, compressed bodies, a rooker-like mouth, and hind legs formed for leaping; they live principally upon the bodies of other animals. (See EPIZOA.) At the end of this order may be mentioned the genus nyete- r'll'm (Latr.), the spider fly, a wingless insect "mi: a spider; the small head seems a IIM-IV tub. -rcle on the anterior and dorsal por- tion of tin- thorax; the eyes are like minute grains; the thorax is semicircular ; the anten- nas are extreim-1 y >hort, inserted close together, and immediately in front of the eyes. These flies nestle in the hair of bats, among which they move with great rapidity ; according to Col. Montagu, when they suck the blood of bats they are obliged to place themselves on their backs on account of the dorsal position of the head. This last division of the diptera is not produced from eggs deposited in the usual manner, but the larva is hatched and de- veloped within the body of the mother, and is not born till it arrives at the state of pupa; hence these genera have been called piipipara by Latreille. The pupa when born is nearly as large as the parent, enclosed in a cocoon, the altered skin of the larva at first soft and white, but soon growing hard and brown ; it is notched at one end, where the mature insect escapes. The genera of diptera make up for their small size by their countless swarms. DIFTTCHS (Gr. dfarvxa, from d/f, twice, and TTTvcceiv, to fold), tablets anciently used for civil and ecclesiastical purposes. Among the Romans and Greeks, the term at the com- mencement of the Christian era designated two tablets united by a hinge, and used as a note book. Even when several tablets or leaves were included between the ornamented covers, they were still called diptychs. The tablets were made of ivory, wood, or metal, and some- times of slate or papyrus, or of gold and silver. The external faces were more or less orna- mented ; the interiors were smooth, so as to re- ceive a coating of wax, or to admit leaves of parchment or papyrus. They were carried suspended to the belt or wrist ; served for epis- tolary correspondence (in which case they were sealed by the writer before being sent to their destination) ; were presented as gifts by con- suls and other high dignitaries to the emperors and senators, and to their friends and relatives ; and were even distributed by them among the people on the occasion of the public games, &c. The oldest consular diptychs known bear the date of A. D. 405, and are attributed to Stilicho. In liturgical usage the diptychs were public lists or tables, which in the early church were read by the deacon from the ambon du- ring the celebration of the liturgy. They con- tained, in so many separate columns or leaves, the names of the persons who made " the offer- ing" that day ; those of the chief personages, lay and ecclesiastical, in communion with that particular church ; the names of the saints, martyrs, and confessors of the faith ; and those of the faithful who had departed this life in the orthodox communion. Hence, to have the name of any person, living or dead, erased, from the diptychs, was equivalent to an act of excommunication. In art the name diptych is given to two panels united by a hinge, whose interior surface is painted. It is common to meet with such diptychs containing on one side the angel Gabriel, and on the other the Virgin Mary- receiving his salutation. When there is a large central compartment, with two side panels folding over it, it is called a triptych. Such is the celebrated Domlild or altarpiece