. Injurious and useful insects; an introduction to the study of economic entomology. Insects; Beneficial insects; Insect pests. ^. i88 INJURIOUS AND USEFUL INSECTS flies, gall-flies). Mouth-parts of adult adapted for biting, or for biting and sucking. There are usually two pairs of un- equal, membranous, rather few-veined wings, which are some- times wanting. The female is provided with saws, a u^^ sting, or an ovipositor. Mn OETHOPTERA Structural peculiarities. — Orthoptera are never very minute, and some Fig. 98.—Diagram of mouth-parts of bee. of them are among the largest of insects. The or

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. Injurious and useful insects; an introduction to the study of economic entomology. Insects; Beneficial insects; Insect pests. ^. i88 INJURIOUS AND USEFUL INSECTS flies, gall-flies). Mouth-parts of adult adapted for biting, or for biting and sucking. There are usually two pairs of un- equal, membranous, rather few-veined wings, which are some- times wanting. The female is provided with saws, a u^^ sting, or an ovipositor. Mn OETHOPTERA Structural peculiarities. — Orthoptera are never very minute, and some Fig. 98.—Diagram of mouth-parts of bee. of them are among the largest of insects. The organisation generally conforms pretty closely to that of the cockroach (Lessons 2, 3, 4, and 36). The wings form externally, instead of being telescoped into the body; they often increase by slow degrees, the new wings being crumpled up within the preceding ones, and liberated at the next moult. They are often useless for flight, sometimes wanting altogether; in other cases only the fore or only the hind pair are de- veloped, or wings appear in one sex only. In the Saltatoria (leaping Orthoptera), the wings may be largely subservient to sound-production, the chirping organ being variously con- structed in the different families. In Acridiidse the inner face of the hind thigh is rubbed against the roughened outer face of the fore wing. In Locustidse the bases of the fore wings are rubbed together; the inner surface of the left wing bears a file, and the outer surface of the right wing a prominent edge, whose vibration sets up a musical note; a transparent area adjacent to the vibrating edge appears to act as a resonator, and to enforce the sound. Both of the fore wings bear files in Gryllidae. The musical organs are possessed only by the male insects, though the females may be provided with non-functional vestiges. Auditory organs are very fre- quent in both sexes; they occur on the fore tibia (Locustidse and Gryllidse) or on the dorsal surface of the first abdominal segment