Download Orthoptera

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Orthoptera
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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
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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,
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Orthorhombic pyroxene
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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
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antenna
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tegmen
pronotum
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cercus
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subgential
plate
auditory
spiracle
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maxillary
&
labial
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Male Mormon cricket, Anabrus simplex, showing some key morphological
features of
Orthoptera. (Reprinted from D. T. Gwynne, Katydids and Bush-Crickets:
Reproductive
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c 2001 by Cornell University. Used
Behavior and Evolution of the Tettigoniidae. Copyright 587
by permission of the publisher, Cornell University Press.)
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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.
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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,
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