Caelifera

Acrididae

7.23. Representative Recent Orthoptera. Not to the same scale.

7.24. Katydid (Tettigoniidae) mimicking lichens on a tree trunk in Costa Rica. Orthopteridans, including stick insects, have some of the best camouflage in nature. Photo: P. J. DeVries.

1975; Burk, 1982; Wagner, 1996; Allen, 1998). This system is analogous to predation of frog-eating bats on the Tungara frog, Physalaemus pustulosus. The male choruses atop a rock to advertise his song. The sexiest part of the song, however, also attracts the frog-eating bat, which snags the frog from its perch. Another such system exists between katydids and bats. Not all insectivorous bats are echolocators. In neotropical forests some bats are silent gleaners, snagging katydids from their calling perches at the tips of branches. Tropical forest katydids possess an odd cycle of momentary bursts of calls interspersed by minutes of silence - apparently an adaptation against bat predation. Katydids in clearings and in Old World forests (which do not have such bat gleaners) have songs that are more continuous.

Today, orthopteran songs are best appreciated at night in a tropical forest. A cacophony of squeaks, clicks, stutters, and high-pitched whines mixed with the calls of frogs nearly drown out any other noise. Triassic forests, however, were devoid of birds, and other than the occasional groans and squeaks of tetrapods, most song probably derived from the resonant clacking of titanopterans, backed by trills of haglids and the chirping of early gryllids. The structure of the wing can allow some prediction as to the nature of songs produced by extinct ensiferans, but few studies have been undertaken. The most interesting to date is that of Rust et al. (1999) on the Paleocene tettigoniid, Pseudotettigonia amoena, from

Denmark. There is a close relationship between the size of the area of the mirror and the frequency of the sound in Recent Tettigoniidae, just as small drums generate higher frequency sounds and a bass kettle drums produces a low sound. Among tettigoniids, Pseudotettigonia was a baritone.

Besides their songs, Orthoptera are also well known as pests, a distinction based on just a few species. Though most orthopterans are generalist phytophages, most families are of no particular concern to agriculture, but the most devastating species are in the family Acrididae (Caelifera). Some acridids - the plague locusts - have solitary and gregarious phases, the latter of which form enormous "clouds" that number into the tens to hundreds of millions of individuals. Such species are extreme generalist feeders; they don't specialize on crop-plant species, but crops simply offer concentrated food resources and are thus natural targets. Today the most problematic plague species are the desert locust, Schistocerca gregaria, and the migratory locust, Locusta migratoria, particularly in northern Africa. Some swarms of the former species have been calculated to number near

7.25. Another camouflaged katydid, which mimics moss in Central America. Photo: P. J. DeVries.
7.26. Leaf katydid camouflaged among dead leaves on the floor of a Panamanian forest. The wings of pseudo-phylline katydids, like this Mimetica, are remarkably leaflike, complete with leaf veins, splotches, and even chew marks. Photo: P. J. DeVries.

50 billion individuals and to cover thousands of square miles. The most devastating swarm in recent history was a 1949 plague in California that resulted in 3,000 square miles of destruction. Eventually the feeding frenzies created by swarming locusts result in the denuding of the foliage; individual locusts then begin to starve, leaving locust corpses strewn across the landscape - the single most impressive example of the extent of insect biomass. Swarms can be carried by the wind and swept out to sea, or even dumped onto glacier surfaces, leaving frozen locusts preserved in the ice. Various other orthopterans are also crop pests, but none instill the same level of fear as locust swarms. It is little wonder why early civilizations were so fearful of locusts and envisioned them as a plague imposed by a wrathful god.

Like the stick insects, many Orthoptera are cryptic in coloration and body structure, resembling foliage or bark substrate (Figures 7.23 to 7.25, 7.27, 7.28). Some of the most remarkable are the Pseudophyllinae, which resemble dried leaves complete with leaf veins, splotches, and chew marks (Figure 7.26). This crypsis is so effective that even seasoned entomologists miss these katydids sitting in plain sight. Aposematic coloration is also common throughout the order. Some of the most peculiar morphologies are found among wingless species that have specialized for living in the soil or in caves. For example, the famous cooloola monster (Stenopelmatidae: Cooloolinae) was hesitatingly placed in Orthoptera when first discovered, owing to its odd anatomical construction even for an ensiferan (Rentz, 1980).

Another extreme example is the Myrmecophilidae (ant crickets), which are small, wingless, microptic, and flattened, adapting them well to a life as inquilines in the nests of ants.

Of all polyneopterous orders, the Orthoptera, perhaps not surprisingly, has the most extensive geological record, second only to that of the roaches and roachoids (Dictyoptera, "Blattodea"). However, Paleozoic Orthoptera, historically placed in Ensifera (e.g., Oedischiidae in Ensifera: Carpenter, 1992), are perhaps a stem group that gave rise independently to the two suborders. Families of this stem group ("oedis-

7.27. A katydid suspended from a branch in Panama, encrusted with lichen-like markings. Another katydid, which has just molted, is behind it. Photo: P. J. DeVries.
7.28. A long grasshopper, camouflaged among palm fronds. Photo: P. J. DeVries.

chioids") persisted well into the Late Mesozoic. By the end of the Permian and the Early Triassic, there is the first definitive evidence of the suborders Ensifera and Caelifera. Bethoux et al. (2002) have recently described an ensiferan from the Late Permian of France that may be a sister group to all other members of the suborder, while the earliest definitive Caelifera come from the Triassic of Asia, Australia, and Europe (Tillyard, 1922b; Sharov, 1968; Jarzembowski, 1999) as well as the Early Jurassic of England (Whalley, 1985; Zessin, 1983). Early Permian families such as Permoraphidiidae and Permelcanidae have at times been considered to be ensifer-ans (e.g., Kukalova-Peck, 1991) but may be stem-group Caelifera, with the extinct family Elcanidae (cover, Figure 7.29) closest to true caeliferans (Bethoux and Nel, 2002). A complete synthesis of fossil Orthoptera, or Orthopterida, has yet to be achieved, the most extensive treatments being those of Zeuner (1939) and Sharov (1968).

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