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602 Orthoptera 379 380 381 382 383 384 385 386 387 body they point backward. Males are smaller than the corresponding females. A few species, however, are hermaphroditic. After insemination the eggs develop in the female and form ciliated larvae. When they are liberated, these larvae invade new individuals of their host and then disaggregate, liberating germinal cells which give rise to new plasmodia. See MESOZOA; REPRODUCTION (ANIMAL). Bayard H. McConnaughey 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 Orthoptera An order that includes over 20,000 species of terrestrial insects, including most of the “singing” insects, some of the world’s largest insects, and some well-known pests. Most species of Orthoptera (from “orthos,” meaning straight, and “pteron,” meaning wing) have enlarged hind legs adapted for jumping. These include grasshoppers and locusts (in the suborder Caelifera, a mainly diurnal group); and the crickets, katydids (bush-crickets), New Zealand weta, and allied families (suborder Ensifera, which comprises mainly nocturnal species). Orthoptera share with other orthopteroid insects, such as mantids and stick insects (now in separate orders Mantodea and Phasmatodea), gradual metamorphosis, chewing mouthparts, and two pairs of wings, the anterior pair of which is usually thickened and leathery and covers the fanwise folded second pair. Wings are reduced or absent in many species. Characters that define the Orthoptera as a natural group (the inclusive set of all species stemming from a common ancestor) are the jumping hind legs, small and wellseparated hind coxae (basal leg segments), a pronotum with large lateral lobes, and important molecular (genetic) characters. Food habits range from omnivorous to strictly carnivorous or herbivorous. Habitats are nearly all terrestrial, including arctic-alpine tundra and tropical areas with aquatic floating plants. Female orthopterans usually lay their eggs into soil or plant material. There are no parasitic species, but a few crickets live as cleptoparasitic “guests” in ant nests. Stridulation and mating. Males of many species are outstandingly noisy or musical. Their songs typically function in obtaining mates. In some species females move to the singing male, and in others a female answering song is involved in pair formation. Males may interact with bouts of singing until one or the other moves away. Song frequencies can range from the audible to the very high ultrasonic. Song patterns typically consist of a complex species-specific series of clicks, buzzes, or musical chirps produced by stridulation, the rubbing of a movable bowlike structure over a precisely arranged series of pegs or ridges. Grasshoppers (Acridoidea) stridulate by rubbing the hind femora against the outer wings, whereas crickets (Gryllidae), katydids (Tettigoniidae), and humped-winged crickets (Haglidae) rapidly rub the forewings together. Some wingless species stridulate with the overlapping edges of abdominal segments or the mandibles. There are at least 20 different mod- ifications of surfaces for acoustical communication, including fanlike snapping of brightly colored hindwings in flight (some grasshoppers). Hearing organs are similarly diverse in form and location. In the grasshoppers, the first abdominal spiracle is modified as a tympanum, whereas the crickets, katydids, and haglids have small tympanic membranes and acoustic receptor cells set into the front tibiae which are connected via the tracheal system to a specialized thoracic spiracle. There are many species of grasshoppers and crickets, however, that lack specialized sound-producing and -receiving organs. Signal communication in these species may be tactile, visual, or olfactory. See ANIMAL COMMUNICATION; PHONORECEPTION. Sound production and later stages of mating behavior have been the focus of much behavioral research. In particular, male orthopterans are known for their nuptial gifts, which are consumed by females. Examples are specialized expendable wings and leg spines, edible substances attached to sperm packages (spermatophores), and dorsal gland secretions of many katydids and crickets, and male glandular secretions absorbed in the female reproductive, tract in some grasshoppers. Such donations by males can be costly and can mediate sex-role reversals when females compete to mate and acquire important nuptial offerings from males. See REPRODUCTIVE BEHAVIOR. Suborder Ensifera. The first ensiferans appear in the fossil record in the Permian. Three superfamilies are commonly recognized in this natural group: Grylloidea (true crickets and allies), Tettigonioidea (katydids, haglids, and allies), and Gryllacridoidea (camel crickets and allies). Based on analyses of morphological and anatomical characters showing only two natural groups of ensiferans, some authors recognize only the first two superfamilies. Ensiferan antennae are usually longer than the body. Most species are nocturnal, and the night-time stridulation of katydids, crickets, and weta can be very loud, especially when males chorus. The ovipositor is long and sword-shaped, and often bores holes in soft wood, bark, living plant stems, or hard-packed soil to lay eggs singly. Tettigoniidae (katydids and bush-crickets) and Gryllidae (true crickets) are the most widespread and diverse families. Many species in both families share with acridoids the completion of the life cycle (egg to adult) in one year, and the use of microhabitats in vegetation (many other ensiferan species have life cycles longer than a year and use burrows and crevices as microhabitats). Many katydids are cryptically shaped and colored, some so similar to leaves that decay spots and insect-chewed margins are mimicked. A major western North American pest is the flightless Mormon cricket (see illustration), dense groups of which can reach several kilometers in length and cover many miles, damaging crops along the way. True crickets (Gryllidae) are ground-, tree-, or bush-dwelling, relatively chunky insects with a needle-shaped ovipositor. Members of the genera Acheta, Teleogryllus, and Gryllus are easily reared, 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 Orthorhombic pyroxene 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 important laboratory animals, and a standard bait and vertebrate food item. Although they can occur in large populations, they are not usually serious pests. However, some mole crickets (Gryllotalpidae) are serious pests of tropical crops. Other ensiferan families include many fossil forms and some bizarre living forms, most of which are flightless. Anostostomatidae includes the giant weta of New Zealand (large specimens can be 30– 40 grams, or 1.1–1.4 oz, in weight) and related, sexually dimorphic weta and king crickets of New Zealand, Australia, and South Africa, in which males fight using tusks or long mandibles. The North American Jerusalem crickets (Stenopelmatidae) are a diverse group of large-headed desert-inhabiting species. The camel and cave crickets, including cave weta of New Zealand (Rhaphidophoridae), are common in caves and damp forests of most continents. Most of these ensiferans are wingless. In contrast are the hump-winged crickets (Haglidae), which comprise a few species inhabiting the forests and high sage of the North American Rockies and the mountains of temperate Asia. One species, the only nocturnal singing insect at high altitudes, stridulates at the lowest ambient temperature known for any insect, −2◦C (28◦F). Suborder Caelifera. This is a natural group that shares a number of characters, including an ovipositor with only four functional valves at the end of the abdomen. In many species, egg laying is accomplished by working the abdomen slowly into the soil and laying eggs in groups. In some grasshoppers the eggs are surrounded by a foamy matrix. Other characteristics that define Caelifera as a natural group are antennae composed of less than 30 segments (being typically less than half the length of the body) and certain genetic characters. There are eight superfamilies: Tridactyloidea (false and pygmy mole crickets and sand gropers); Tetrigoidea (pygmy grasshoppers and grouse locusts); Eumastacoidea (monkey grasshoppers and false stick insects); Pneumoroidea (flying gooseberries, desert longhorned grasshoppers, and razor-back bushhoppers); Pamphagoidea (rugged earth hoppers and true bushhoppers); Acridoidea (grasshoppers and locusts); and Trigonopterygoidea. Most caeliferans are diurnal. The most familiar and diverse are short-horned grasshoppers (Acridoidea) which tend to be active in bright sunshine. Some species are cryptic, mimicking stones, debris, and grass stems. Although most species of grasshoppers are never abundant enough to become agricultural pests, some have little-understood cycles of abundance that sometimes phase together to become major crop-destroying events, especially in drier regions of North America, Africa, and Australia. In some years, plague locusts such as Locusta migratoria, Schistocerca gregaria, and others migrate hundreds of miles from an outbreak center to devastate thousands of acres of crops in the tropics and subtropics. Remarkable structural and behavioral changes occur from the solitary generation to the migratory generation. Several North American species of Melanoplus 603 568 569 antenna 570 tegmen pronotum 571 572 573 574 575 cercus 576 577 578 579 580 subgential plate auditory spiracle 581 maxillary & labial 582 palps 583 584 585 Male Mormon cricket, Anabrus simplex, showing some key morphological features of Orthoptera. (Reprinted from D. T. Gwynne, Katydids and Bush-Crickets: Reproductive 586 c 2001 by Cornell University. Used Behavior and Evolution of the Tettigoniidae. Copyright 587 by permission of the publisher, Cornell University Press.) 588 have a latent ability to shift to a migratory phase, though natural outbreaks have occurred only historically, in a species which is now thought to be extinct. The plague locusts are large, hardy insects, extensively used for neurophysiological and general physiological studies. Pygmy mole crickets and sand gropers (Tridactyloidea) have evolved specialized front legs for digging that resemble the front legs of true mole crickets. Some burrowing sand gropers can be pests of crop fields in Australia. Pneumoroids include the remarkable bladder grasshoppers of Africa, which lack a tympanum in the abdominal ear yet the very loud male stridulation can be detected by females at a distance of almost 2 km (1.2 mi). See INSECT PHYSIOLOGY; INSECTA. Darryl T. Gwynne; Robert B. Willey Bibliography. J. L. Capinera, R. D. Scott, et al., Field Guide to Grasshoppers, Katydids, and Crickets of the United States, Cornell University Press, Ithaca, NY, 2004; R. F. Chapman and A. Joern (eds.), The Biology of Grasshoppers, Wiley, 1990; L. H. Field (ed.), The Biology of Wetas, King Crickets and their Allies, CABI International, Walling ford, 2001; S. K. Gangwere, M. C. Mulalirangen, and M. Mulalirangen (eds.), The Bionomics of Grasshoppers, Katydids and Their Kin, CAB International, Oxford, 1997; D. T. Gwynne, Katydids and Bush-crickets: Reproductive Behavior and Evolution of the Tettigoniidae, Cornell University Press, Ithaca, NY, 2001; J. A. Marshall and E. C. M. Haes, Grasshoppers and Allied Insects of Great Britain and Ireland, Harley Books, Colchester, 1988; D. C. Rentz, Grasshopper Country: The Abundant Orthopteroid Insects of Australia, University of New South Wales Press, Sydney, 1996. 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615 616 617 618 619 620 621 622 623 624 625 626 Orthorhombic pyroxene A group of minerals having the general chemical formula XYSi2O6, in which the Y site contains iron (Fe) or magnesium (Mg) and the X site contains Fe, 627 628 629 630