The =Elder Thrips= (_Thrips sambuci_) lives in elder, and sometimes also multiplies in very young field beans, the leaves of which blacken and shrivel up in consequence. The =Flax Thrips= (_Thrips lini_) often injures flax. EIGHTH ORDER: =Diptera= (FLIES). Mouth-parts elongated, adapted for sucking or piercing. Fore wings developed, rarely absent. Hind wings absent, as such,—altered into club-like bodies (balancers or halteres) often covered with scales. Metamorphosis complete. Larvæ always legless; most have biting mouth-parts and no distinct head (maggots); the head-bearing dipterous larvæ possess similar mouth-parts. The last become obtectate pupæ (p. 93), while the headless larvæ become pupæ within the larval skin. Family: =Culicinæ= (_Gnats_). Slenderly built, with long, thin legs. An elongated piercing proboscis in the female. The male with feebly developed mouth-parts, and feather-like antennæ. Both sexes suck up water and plant juices, and the female blood as well; hence only the latter bites, especially at night. They hybernate in the adult condition in cellars, barns, etc. The female lays 250 to 300 eggs on any floating object in stagnant water (pools, ditches, water-vessels). The larvæ (with large head, well-developed prothorax, and a breathing-tube on the abdomen) live in water, as do the pupæ. Several generations annually; especially in damp summers and districts where the draining of the soil leaves much to be desired. Although sand flies torment our domestic animals more than gnats, yet these also may be very troublesome to them. They principally attack the less hairy parts of the body (inner side of the ears, nose, mouth, corners of the eye, arms, sexual parts). _Remedies_: Thorough draining of the soil. Washing the domestic animals to be protected with a vinegar extract of walnut leaves; rubbing with walnut leaves. Wherever possible, any sores should be covered up, as they attract gnats, sand flies, and flies; or the skin near them may be painted with turpentine or very dilute carbolic acid. This is the less to be neglected, as several kinds of flies eagerly lay their eggs in the sores of domestic animals. Family: =Gallicolæ= (_Gall Gnats_). [Illustration: FIG. 110.—The Wheat Midge (_Cecidomyia tritici_), female. ]