Page:The American Cyclopædia (1879) Volume VI.djvu/136

128 DIPTERA lished a pamphlet regarded as heretical, he was expelled from the country and soon afterward died. He acquired much scientific knowledge and made some valuable discover- ies. The main point of his doctrine was that Christianity consists solely in the practice of virtue, of self-denial, and love for mankind. He published his writings under the name of Christianas Democritus (collected under the title of Eroffneter Weg zum Frieden mit Gott vnd alien Creaturen, Amsterdam, 1709; en- larged ed., Berleburg, 1743). He attracted much notice in his day in Sweden and Ger- many, and is frequently mentioned by Sweden- borg in his " Spiritual Diary." His biography was written by Ackermann (Leipsic, 1781), and Buchner has given a memoir of him in the HistorUches TaschenbucU for 1858. DIPTERA (Gr. 61$, twice, and KTep6v, wing), an order of insects, containing the fly, mos- quito, &c., characterized by two wings, two knobbed threads (halteres, balancers or pois- ers) behind the wings, and a horny or fleshy proboscis. They undergo a complete trans- formation ; the larvae, usually called maggots, Larva and Imago of the Bot Fly of the Ox (Hypodermia bovis). have no feet, and have the breathing holes generally in the posterior part of the body ; the pupae or nymphs are either incased in the dry skin of the larvae, or naked, showing the wings and legs free and unconfined. The head is large, globular, connected with the body by a very slender neck, and is capable of a con- siderable pivot-like motion ; the greater part, especially in the males, is occupied by the brilliant compound eyes, the single ocelli, when they exist, being on the top of the head. Under the head is the proboscis or sucker, which in some kinds can be drawn up and concealed in the mouth ; it consists of a long channel, ending in two fleshy lips, and enclo- sing on its upper side from two to six fine bris- tles, sharp as needles, and making the punc- tures so familiarly known in the case of mos- quito bites; as this apparatus takes the place Of the jaws of other insects, these wounds may properly be called bites. The saliva which flows into the wounds causes the well known swell- ing and itching. The sheath serves to main- tain the lancets in position, and the latter hav- ing made their punctures form a groove along which the vegetable or animal fluids rise by the suctorial power of the insect and by capil- lary attraction. In the flies which only lap their food the proboscis is large and fleshy. The antennae in the gnats are long and many- jointed, in the flies short and thick, at the base of the proboscis. The wings are generally horizontal and delicate, with many simple veins ; the posterior wings are metamorphosed into the balancers or poisers. Some entomologists, as Latreille, think the poisers do not corre- spond to posterior wings, but are vesicular ap- pendages connected with the posterior respi- ratory tracheae of the chest. Just behind the wing joints, and in front of the poisers, are two small convex scales, opening and shutting with the wings, and called winglets. The thorax is often the hardest part of the insect, composed principally of the mesothorax. The abdomen is not always united to the thorax by the whole of its posterior diameter, and in many females ends in a retractile jointed ovipositor. The legs, six in number, are usually long and slender, with five articulate tarsi and two claws at the end, besides two or three little cushion-like expansions, by means of which they are able to ascend the smoothest surfaces and to walk with the back downward with perfect security. According to Marcel de Serres, the dorsal vessel (the heart) in diptera is narrow and its pulsations are frequent. Respiration in the adult is carried on by vesicular and tubular tracheae. The nervous system consists of an aggregate of cerebral ganglia, and in some of nine other ganglia, three in the thorax and six in the abdomen, connected by longitudinal simple commissures or cords ; the larvae have usually one more pair of ganglia than the adults, and have the commissures often double. The proboscis being the transformed under lip, often geniculate, the perforating bristles may be regarded as maxillae, mandibles, and tongue. In those larvae which have a distinct head, as in the mosquito, the jaws are arranged for mastication, though some of the pieces are wanting; but in the acephalous maggots the mouth is suctorial. Communicating with the gullet is a thin-walled vesicle, the sucking stomach, in which the fluids swallowed are temporarily deposited ; the stomach proper is long and narrow, and makes many convolu- tions in the abdomen. The end of the intes- tine is short, muscular, and pyriform. The uriniferous vessels are long, and generally four in number, opening into the lower extremity of the stomach ; the ovaries consist usually of many short three- or four-chambered tubes, terminating in a short or a convoluted oviduct ; the testicles are two, simple, and generally oval or pyriform, with long vasa deferentia ending in the ejaculatory duct in common with two simple accessory mucous glands, and with horny valves enveloping the projecting copu- latory organ. The larvae or maggots are