Orthopterida

Perhaps allied to Plecopterida by the prognathous head (secondarily hypognathous in Orthoptera), fusion of the premen-tal lobes, and neuroanatomical traits (Ali and Darling, 1998) is the Orthopterida. This group in its strict sense is relatively free of controversy and comprises the two living orders Orthoptera and Phasmatodea and the two extinct orders Titanoptera and Caloneurodea. Orthopterids have the second valvulae reduced, concomitant development of the gonoplac (i.e., the ill-named third valvula) as the functional ovipositor, and an enlarged precostal field in the forewing. Attempts to incorporate other orders into the Orthopterida, such as Grylloblattodea or Embiodea, are not strongly supported at present. Embiodea has at times been argued to be the living sister group of the walking-sticks owing to the presence of an operculum on the egg as well as certain mouthpart muscles (Kristensen, 1975; Tilgner, 2000). Despite these similarities, they must be interpreted as convergence against the larger body of evidence showing that Embiodea is within Plecopterida and sister to Zoraptera (see preceding discussion), and that Phasmatodea is closely related to Orthoptera (Kristensen, 1975; Flook and Rowell, 1998; Wheeler et al., 2001). Orthopterida is perhaps related to Grylloblattodea and Mantophasmatodea as these orders exhibit a similar development of the gonoplac over the second valvu-lae, although to a much lesser degree. The Polyorthoptera incorporates the Orthopterida, Grylloblattodea, Mantophas-matodea, and perhaps the Dermaptera.

Possibly included in this group is the enigmatic fossil family Chresmodidae. Chresmodids contained a single known genus and four species (Engel and Grimaldi, in prep.) that superficially resembled water striders (Hemiptera: Gerridae) with robust bodies and extremely long legs. Like water striders, chresmodids were apparently aquatic and may have skated across water surfaces, or perhaps treaded over vegetation exposed at the water surface. Chresmodids are known from the Late Jurassic of Solnhofen, Germany, and the Early Cretaceous of Spain (Montsec) (Figure 7.4), China, and Brazil (Santana Formation) (Figure 7.5). The difficulty of placing Chresmoda is highlighted by its classification over the last 164 years - at times being considered related to or in Gerridae (Hemiptera), Mantodea, Paraplecoptera, and Phasmatodea. Handlirsch (1906b) was the first to move the chresmodids into the Phasmatodea, and Martynov (1928) later erected a separate suborder, Chresmododea, believing them to be stem-group phasmatodeans (a position also held by Sharov,

7.4. Chresmoda aquatica (Chresmodidae) from the Early Cretaceous of Spain. Chresmodidae resembled modern water striders, but these giant, apparently semiaquatic insects were relatives of Orthoptera and Phasmatodea. Photo: X. Martinez-Delclos.

1968). Popov (1980), highlighting the fact that chresmodids were aquatic and resembled gerrids (like Oppenheim, 1888, before him), considered the family as belonging to the Gerromorpha (Hemiptera). However, Ponomarenko (1985) noted the presence of cerci and pentamerous tarsi, traits that excluded the Chresmodidae from the Paraneoptera, and

7.5. Chresmodidae from the Early Cretaceous of Brazil, which is the first Western Hemisphere species of this enigmatic, Mesozoic lineage of insects. AMNH; body length 37 mm.
7.6. Phylogeny of Plecoptera. Thick lines indicate the extent of known fossils. Based on Zwick (1998).

alternatively placed the family in the extinct Paraplecoptera (which are stem-group polyneopterans). Rasnitsyn (in Rasnitsyn and Quicke, 2002) considered chresmodids as of uncertain affinity among polyneopterans, dismissing any relationship with Phasmatodea.

PLECOPTERA: THE STONEFLIES

Stoneflies are unique among basal neopterans for their aquatic life history, the nymphs of which live entirely in freshwater. Nymphs of a few species are terrestrial, but they live in very wet or moist habitats. Owing to the unique development of strong abdominal muscles, nymphs are capable of swimming via lateral undulations of the body, much like fish (Zwick, 1980, 2000). Species are principally detritivores or omnivorous; few species are strictly carnivorous. Many nymphs are grazers, gleaning the surfaces of stones for algae. The approximately 2,000 species are segregated into 16 mod ern families, which divide themselves into Laurasian and Gondwanan lineages (Zwick, 1973, 2000) (Figure 7.6). Major works on the order include those by Claassen (1940), Illies (1966), and Zwick (1973, 2000).

Adult stoneflies are primitive-looking neopterans (Figure 7.7), which has contributed to the notion that the order is basal among neopterous insects. As discussed earlier, however, the Plecoptera possess some presumed apomor-phies with other polyneopterous groups. Additionally, an aquatic life history for stonefly nymphs (Figure 7.8) is often considered to be primitive owing to aquatic naiads in Ephemeroptera and Odonata, when in fact it may partly define monophyly of Plecoptera. One hypothesis of Plecoptera as nested within Polyneoptera (e.g., Ali and Darling, 1998; Wheeler et al., 2001) suggests a transition to aquatic living in this group, which is of significant interest. Various aspects of stonefly biology have been equated with the groundplan condition for all Neoptera, and some studies have focused on stoneflies as models for understanding the

Chresmodidae
7.7. Representative adults of Recent Plecoptera. Not to the same scale.
Teratembiidae Nymph
7.8. A Plecoptera nymph.

origins of flight within insects (e.g., Marden and Kramer, 1994, 1995; Thomas et al., 2000). Certainly, the different gill types alone in Plecoptera, Ephemeroptera, and Odonata suggest independent origins of aquatic lives. Furthermore, the placement of Plecoptera within Polyneoptera erodes the notion that stoneflies can be considered early fliers even if aquatic naiads are primitive.

Some Plecoptera oviposit during flight, merely dropping masses of eggs from the air into the water or skimming over the water surface and "washing" eggs off of their venter. The ovipositor is vestigial and is cited as a defining specialization for the order (Willmann, 1997; Zwick, 2000), but here it is considered as a more inclusive trait uniting Plecoptera with Embiodea and Zoraptera. A few species with secondarily developed ovipositors (e.g., Notonemouridae) oviposit into wet crevices. Other, less visible, synapomorphies for the order include the lopped gonads, where the anterior apices of the left and right ovaries and testes are fused in the middle (Zwick, 1973), and the presence of an accessory circulatory organ ("cercal heart") (Pass, 1987; Zwick, 2000). Modern species of the order have three-segmented tarsi, but this is not homologous with the trimerous condition seen in Embiodea, Dermaptera, Timematodea, and some other orders since Paleozoic stem-group Plecoptera had five-segmented tarsi.

The most recent cladistic classification of Plecoptera is by Zwick (2000), which found support for the two traditional suborders or lineages, Antarctoperlaria and Arctoperlaria (Figure 7.6). Limited cladistic analyses have suggested para-phyly of Antarctoperlaria, by placing Gripopterygoidea (an antarctoperlarian) basal within Arctoperlaria, but these studies require corroboration (Nelson, 1984: reanalyzed by Will, 1995). As alluded to in their names, the two suborders are divided between hemispheres; Antarctoperlaria in the Southern Hemisphere and Arctoperlaria in the Northern. Colonization of the Southern Hemisphere has occurred in some derived genera of Arctoperlaria - the family Perlidae into South America and the Notonemouridae into Australia, South America, and Africa (Zwick, 2000). The suborders are defined unfortunately by characters that are unknown from fossils or unlikely to ever be preserved as fossils, such as muscles. Antarctoperlaria is supported by the presence of a unique sternal depressor muscle of the fore trochanter and concomitant absence of the typical tergal depressor muscle of this structure as well as the presence of floriform-chloride osmoregulatory cells. Arctoperlaria is defined by "drumming," a behavior of males advertising to females. The male taps on the substrate with the tip of his abdomen, on which he typically has special modifications (called the "hammer") for producing the sound (Zwick, 1973, 1980).

The oldest stoneflies (stoneflies in stone!) are a few groups from the Early Permian, but these likely represent stem-group families paraphyletic to all other Plecoptera. Indeed, families such as Lemmatophoridae had terrestrial nymphs

(Figure 7.9) and, along with others such as Liomopteridae and Probnidae, appear allied to the Plecoptera while ple-siomorphically retaining five-segmented tarsi. At times such families have been grouped into an extinct order, Paraplecoptera or Protoperlaria (e.g., Tillyard, 1928d; Mar-tynov, 1938); however, recognition of such a taxon is premature and is at present defined entirely on the absence of modern stonefly apomorphies. It is possible that paranotal lobes in some of these lineages comprise a defining specialized feature of an early branch of stoneflies (e.g., Lem-matophoridae + Liomopteridae). Like other polyneopterans, the record of the order does not truly develop until the Mesozoic, from which numerous fossils are known, including early representatives of modern families (e.g., Notonemouridae). Permian records for the modern families Eustheniidae and Taeniopterygidae deserve critical evaluation, particularly because these are not basal families for the order (Zwick, 2000). The biogeographical separation of the suborders corresponds to the breakup of Pangea into Laurasia and Gondwanaland during the Late Jurassic, and these groups likely became differentiated during this time period.

7.9. Although the immatures of Early Permian Lemmatophoridae were apparently not aquatic, species such as Lemmatophora typa were primitive relatives of modern stoneflies. YPM 5115; length 8.5 mm.

EMBIODEA1: THE WEBSPINNERS

Webspinners are gregarious insects occurring principally in the tropics, though some extend into warm temperate regions (Figure 7.10). There are approximately 360 described species in approximately nine families (Ross, 1970, 2001, 2003a,b; Szumik, 2004), although the higher classification of the order is presently under investigation, and these figures will undoubtedly change dramatically in the very near future. The foremost features of the order are intimately associated with their biology. Species live in "galleries" produced by silk from glands inside the enlarged fore basitarsi (Figure 7.11). Silk is spun during all nymphal instars and by adults. The silk is extruded through specialized, hollow setae (Figure 7.11) that internally connect to unique glands of ectodermal origin. The tarsi are three-segmented but, as discussed earlier, the trimerous condition is perhaps not homologous with that

1 Lively Wings? Various names abound for this order, the most common of which is Embiidina. Embiidina was favored by authors over Embioptera since the latter was less than truly descriptive. In Greek Embioptera means "lively wing," even though webspinners are anything but spectacular fliers, although it might have been meant as a reference to how males flip their wings over and back. Regardless, several ordinal names are not very meaningful as currently constructed (e.g., Psocoptera, which combines a reference to their feeding habits and their wings!). Although ordinal names are not regulated in zoological taxonomy, family-group names are and the suffix -ina is a standard termination for the rank of subtribe. Thus, the name Embiidina is misleading, suggesting a group within the family Embiidae. Thus, we have adopted the name Embiodea, which avoids the difficulties cited for both of the former names.

seen in Plecoptera and is certainly not homologous with that in Dermaptera or Timematodea.

Another distinctly embiodean trait is the desclerotization of the longitudinal wing veins and the development of blood sinuses in the wings, which are hollows through which hemolymph is pumped. When hemolymph is withdrawn into the body, the wings become flexible and collapse upon themselves, even flipping over the thorax and head during backward movement through the narrow tunnels and chambers of the gallery. When flight is necessary, the wings are made more rigid by filling the sinuses with hemolymph. Females are apterous, while males may possess dehiscent wings.

7.10. A webspinner in its web. Photo: J. Edgerly.
7.11. Scanning electron micrographs of representative webspinners (Embiodea). Silk is extruded from the tips of specialized, hollow setae on the enlarged foretarsus, which houses the silk glands.

Other traits for Embiodea include a prognathous head, closed ventrally by a gula between the submentum and occipital foramen; absence of ocelli; presence of a dorsal, paraglossa flexor muscle in the mouthparts (Rahle, 1970: not well surveyed across the order but also in Phasmatodea); and those traits discussed previously in relation to the overall placement of the order within Plecopterida.

Webspinners are communal, with females taking close care of their offspring (Edgerly, 1987a, 1988). Females may share a composite gallery but participate only in rearing their own young (Ross, 2000b), and, indeed, communal behavior is facultative (Edgerly, 1987b, 1994). Such societies are similar to those of zorapterans, although communal living is obligate within Zoraptera given that individuals separated from colonies do not survive.

The basal family for the order is Clothodidae (Davis, 1939b, 1940; Ross, 1970, 1987; Szumik, 1996; Szumik et al., 2003). Clothodids are restricted to the South American tropics and include the "giants" of the Embiodea (Ross, 1987). Unlike the "higher" webspinners, Clothodidae have

Zorotypus Insect Images
7.12. A webspinner in Miocene amber from the Dominican Republic. Morone Collection, M3473; length 7.5mm Photo: R. Larimer.

symmetrical, unlobed male terminalia and more complete and sclerotized wing venation (Ross, 1987, 2000a). Relationships among the "higher" families are remarkably confused, and the largest family, Embiidae, is paraphyletic if not poly-phyletic (Szumik, 1996; Szumik et al., 2003). Comprehensive work on relationships and classification is desperately needed.

Webspinner fossils are rare. Tertiary fossils derive almost exclusively from mid-Eocene Baltic or Early Miocene Dominican amber (Ross, 1956; Szumik, 1994, 1998) (Figure 7.12), but a single compression fossil is also known from the latest Eocene of Florissant, Colorado (Cockerell, 1908b; Ross, 1984). The Miocene fossil described by Hong and Wang (1987) as a clothodid webspinner, Clothonopsis miocenica, is actually a bibionid fly (Zhang, 1993)! All the Tertiary fossils belong to the families Teratembiidae or Anisembiidae or the polyphyletic family Embiidae. There are only two pre-Cenozoic records for the order, both in mid-Cretaceous amber from Myanmar (Cockerell, 1919; Davis, 1939a; Grimaldi et al., 2002; Engel and Grimaldi, unpubl.) (Figure 7.13). Both Cretaceous species are typical webspinners but represent extinct families, perhaps close to Australembiidae.

Earlier authors attributed several Permian or Early Meso-zoic fossils to Embiodea. For instance, Tillyard (1937b) proposed the suborder Protembiaria for what he believed to be the earliest representatives of the webspinners, Protembia permiana (Protembiidae) from the Lower Permian deposits of Elmo, Kansas. Carpenter (1950), however, demonstrated that these Permian fossils were not webspinners. Similarly, Martynova (1958) proposed an extinct suborder, Sheimiodea, for a Late Permian fossil from Russia that she believed to be a basal webspinner. Again Carpenter (1976: see also Ross,

2000a) intervened, showing that this fossil, like Protembia, preserved no character indicative of Embiodea.

Most recently, a putative webspinner was reported by Kukalova-Peck (1991) from the Permian of Russia, and another was depicted by Rasnitsyn (in Rasnitsyn and Quicke, 2002) from the Jurassic of Karatau. The figure of Kukalova-Peck's specimen is consistent in its overall shape to that of

7.13. The earliest definitive fossil webspinners (order Embiodea) are two species in mid-Cretaceous amber from Myanmar, one shown here. Neither of them is particularly primitive, indicating that webspinners existed much earlier than the Cretaceous. AMNH Bu227; length 5.5 mm.

Embiodea, such as the homonomous wings with narrow bases (though venation is barely depicted) and apparently asymmetrical male genitalia. The latter are not unique to the order (e.g., Grylloblattodea, Zoraptera, Timematodea), and it is not clear whether asymmetry is merely the result of imperfect preservation. Despite its name, Permembia was not considered a relative of Embiodea but instead of the Psocoptera (Tillyard, 1928c, 1937b). Permian webspinners are not impossible, but they seem unlikely.

The Jurassic specimen is more consistent with the presumed Mesozoic age of the order, but again an absence of defining features prevents definitive assignment of the Karatau fossil. In fact, the fossil possesses a large anal fan in the hind wing, unmodified tarsi, and unmodified hind femora, so it is clearly not a true webspinner. Of those fossils definitively assigned to Embiodea, all are derived compared to the Clothodidae. Thus, basal divergence in the order must be at least prior to the appearance of Burmitembia and others in the latest Albian to Cenomanian (Engel and Grimaldi, unpubl.), perhaps extending to the Early Jurassic. Pre-Cretaceous webspinners will be difficult to recover owing to the poor preservation of their soft bodies and wings in rocks, and as of yet insect-bearing ambers prior to the Early Cretaceous are unknown.

ZORAPTERA: THE ZORAPTERANS

Zorapterans are minute insects, ca. 3 mm long (0.12 in.), superficially resembling barklice (Psocoptera) (Figure 7.14). They live gregariously under the bark of decaying logs or within termite nests, where they principally feed on fungal hyphae, nematodes, or minute arthropods like mites and Collembola (Engel, 2003a, 2004b). Despite being physically obscure, they have been of considerable evolutionary interest regarding relationships. The zorapterans presently comprise 32 modern species, all classified into a single genus (Zorotypus) and family (Zorotypidae), distributed pantropi-cally. Attempts to divide extant Zorotypus into multiple genera (e.g., Kukalova-Peck and Peck, 1993; Chao and Chen, 2000) have rendered Zorotypus paraphyletic, creating an unnatural classification, so the traditional system is retained (Engel and Grimaldi, 2000, 2002; Engel, 2003e). Where known, each species has two adult morphs - an eyed, winged form (i.e., alates) and an eyeless, apterous one. Zoraptera monophyly is well established based on the peculiar wing venation (Figure 7.15); two-segmented tarsi (with the basal segment greatly reduced; the more elongate second segment probably results from the fusion of two segments); peculiar mating via a "mating hook" (even evident in Cretaceous fossils); unsegmented cerci (except in one apomorphic Miocene species); stout metafemoral spines; and moniliform, nine-

segmented antennae. Furthermore, they possess peculiar behavioral traits that help to define the group (Valentine, 1986).

Many authors contend that zorapterans are poor fliers and therefore have limited dispersal abilities (e.g., Huang, 1980; Kukalova-Peck and Peck, 1993). Indeed, zorapteran wings are not well-adapted for flight; however, species live in relatively ephemeral, subcortical habitats. Such habitats suggest that individuals are quite capable of dispersal and also consistent with the dimorphism within species. During the general life of a zorapteran colony, blind, wingless morphs predominate. As the population grows, resources become limited either owing to the natural decomposition of the logs in which they reside or through the consumption of local nutrients by the larger numbers of individuals. Such crowding or nutrient deficiencies trigger the production of fully eyed alates capable of dispersing to new nesting sites; females of these winged morphs probably mate prior to dispersal, thereby accounting for the relatively low abundance of alate males. Once arriving at a new log, individuals shed their wings, the way termites, ants, and some male webspinners do. Dealated individuals can often be found in young colonies. Experimental evidence lends credence to this scenario because both habitat quality and crowding can lead to the production of alates (Choe, 1992). Furthermore, the distributions of various species are increasingly understood to cover large geographic ranges, suggesting some dispersal capabilities (e.g., Engel, 2001d). Little emphasis should be paid to absences in distributions, but despite the intensive efforts of Australian insect surveys, no zorapteran is yet known from the mainland of Australia. A single species has been discovered on Christmas Island (New, 1995), politically an Australian territory but geographically and biologically part of Indonesia and a region where zorapterans are already known to occur. If indeed the order does truly occur in the Australian region, then they would be expected in tropical Queensland or New Caledonia, areas that are typical components of old, relict distributions and particularly those affected by continental vicariance (Engel and Grimaldi, 2002).

Perhaps more than any other polyneopteran order, Zoraptera have puzzled entomologists for decades and fueled considerable debate regarding their relationships to other orders. At one time or another Zoraptera has been considered to be the living sister group to Isoptera (Caudell, 1918; Crampton, 1920; Weidner, 1969, 1970; Boudreaux, 1979), to Isoptera + Blattaria (Silvestri, 1913), Paraneoptera (Hennig, 1953, 1969, 1981; Kristensen, 1975), Embiodea (Minet and Bourgoin, 1986; Engel and Grimaldi, 2000, 2002; Grimaldi, 2001; Engel, 2003a,e), Holometabola (Ras-nitsyn, 1998), Dermaptera (Carpenter and Wheeler, 1999), Dermaptera + Dictyoptera (Kukalova-Peck and Peck, 1993),

7.14. The minute zorapterans, such as Zorotypus hubbardi (Zorotypidae) shown here are dimorphic within each species; colonies predominantly have individuals that are blind and wingless. Zorapterans superficially resemble barklice or termites, but have distinctive mouthparts and enlarged hind femora with stout spines. Phyloge-netic position of the order has been controversial, but they appear closely related to webspinners. Scanning electron micrographs; length 2.5 mm.

Immature Isopteras Wing
7.15. The most primitive known zorapteran, Xenozorotypus burmiticus (Zorotypidae), in mid-Cretaceous amber from Myanmar. AMNH Bu-182; length 1.9 mm; from Engel and Grimaldi (2002).

basal within Thysanoptera (Karny, 1922), or Psocoptera (Karny, 1932); or unresolved among Orthoptera, Phasma-todea, and Embiodea (Kukalova-Peck, 1991). The only other order that has such confusing relationships is the Strepsiptera. Despite the confusion, Zoraptera have been demonstrated to belong to the Polyneoptera (Boudreaux, 1979; Carpenter and Wheeler, 1999; Engel and Grimaldi, 2000) within which a close relationship to the Embiodea is best supported.

Unfortunately, the current geological record of Zoraptera, like Embiodea, is extremely sparse. Until recently, the only fossil Zoraptera known were two species in Miocene amber from the Dominican Republic (Engel and Grimaldi, 2000). Not surprisingly, these species are remarkably modern in appearance, with only Zorotypus goeleti possessing any notably primitive features (i.e., two-segmented cerci). The order is known from only one other fossil deposit. Four species occur in mid-Cretaceous amber from Myanmar, three of which belong to the modern genus Zorotypus (Engel and Grimaldi, 2002) (Figure 7.16). One species, Xenozorotypus burmiticus (Figure 7.15), primitively retains an additional vein in the hind wing, but it is like a modern zorapteran in all other respects, indicating that it is probably sister to all other Zoraptera. Highlighting their essentially modern character, Cretaceous zorapterans occurred in two morphs, with fossils known as both alates and apterous, blind morphs.

7.16. Although 100 myo, Zorotypus nascimbenei (Zorotypidae) and several other zorapterans in Burmese amber are amazingly similar to modern species, attesting to the antiquity of the group. AMNH Bu341; length 1.5 mm; from Engel and Grimaldi (2002).

ORTHOPTERA: THE CRICKETS, KATYDIDS, GRASSHOPPERS, WETAS, AND KIN

The poetry of Earth is never dead: When all the birds are faint with the hot sun, And hide in cooling trees, a voice will run From hedge to hedge about the new-mown mead; That is the Grasshopper's - he takes the lead In summer luxury, - he has never done With his delights; for when tired out with fun He rests at ease beneath some pleasant weed. The poetry of Earth is ceasing never: On a lone winter evening, when the frost Has wrought a silence, from the stove there shrills The Cricket's song, in warmth increasing ever, And seems to one in drowsiness half lost, The Grasshopper's among some grassy hills. -On the Grasshopper and Cricket, John Keats (1795-1821), 30 December 1816

Most polyneopterous lineages consist of a few thousand species (or much less!), but Orthoptera is the only poly-neopteran order with any sizeable diversity, having around 22,500 described species. The order has attracted the attention of humans since antiquity, developing into a "love-hate" relationship. On the one hand, orthopterans have been a source of wonderment for their diversity and soothing songs. Images of raphidophorine cave crickets, for example, have even been drawn onto the walls of caves in southern France by Paleolithic people, along with large mammals. Larger orthopterans are eaten by some indigenous peoples. In China, crickets are kept in tiny bamboo cages as pets and signs of good luck, as they have for millennia, and the chirping of woodland and field crickets is considered more enjoyable than that of a songbird (Laufer, 1927). Conversely, swarms of grasshoppers have been scourges to agriculture.

7.18. Phylogeny of the Orthopterida. Modified from Bethoux and Nel (2002); Phasmatodea after Willmann (2003).
7.17. Aposematic grasshopper nymphs in Costa Rica improve their individual chemical defense by clustering. Some orthopterans, like pygomorphids, defend themselves very effectively with toxic secretions. Photo: D. Grimaldi.

Ancient texts have repeated references to pestilence and plague brought by these insects, perhaps the most famous being those from the Bible: "All thy trees and fruit of thy land shall the locust consume" (Deuteronomy 28:42, King James Version). The order is, indeed, principally phytophagous but carnivorous, predatory species do exist. Major references to the Orthoptera include Uvarov (1928, 1966), Chopard (1938), Otte (1981, 1984, 1994), Gwynne and Morris (1983), Gangwere et al. (1997), Field (2001), Gwynne (2001), and Bethoux and Nel (2002).

Orthoptera have traditionally been divided into two major lineages, presently recognized as suborders, Ensifera and Caelifera (Figure 7.18). Although these have at times been elevated to ordinal status (e.g., Kevan, 1977, 1986; Vickery and Kevan, 1985), this division is based on superficial, phenetic differences between the two suborders. The monophyly of Orthoptera and of extant members in the suborders is

7.19. A female katydid consuming a nuptial meal: a large sper-matophore left by a recent mate. The large packets of sperm are far larger than is needed for fertilization and appear to have evolved as one means of courtship. Photo: P. J. DeVries.

strongly founded and widely supported by both morphological and molecular data (Boudreaux, 1979; Hennig, 1981; Kuperus and Chapco, 1996; Flook and Rowell, 1997, 1998; Rowell and Flook, 1998; Flook et al., 1999; Maekawa et al., 1999; Wheeler et al., 2001). A cryptopleuron, developed from the lateral extension of the pronotum over the pleural scle-rites and desclerotization of the latter, is typical of Orthoptera, though this feature is lost in Proscopiidae (Caelifera). Another famous orthopteran apomorphy is the possession of saltatorial (i.e., jumping) hind legs, with straightening of the femur-tibia articulation for maximal leg extension, and a thick femur packed with muscles. Additional defining features of the order are the hind tibia with paired, longitudinal rows of teeth or spines on the dorsal surface; a horizontal division of the prothoracic spiracle; wings inclined over the abdomen during rest; and a reversal in the orientation of nymphal wing pads during later instars (Kristensen, 1991). Similarly, although monophyly of Ensifera (crickets, katydids, wetas, and their relatives: Figure 7.19) has been doubted, cladistic studies have consistently recovered them as a natural group, supported principally by the long, flagellate antennae (e.g., Flook and Rowell, 1997, 1998), but this group might eventually prove to be plesiomorphic when compared to Paleozoic orthopterans. The distinctive protib-ial auditory organs of ensiferans are believed to have evolved twice within the suborder and therefore do not define the entire group (Gwynne, 1995). Ragge (1977) and Gwynne (1995) both support two monophyletic branches within

Ensifera, the Tettigoniida and Gryllida. Caelifera (grasshoppers, locusts, and their relatives) is similarly monophyletic and is presently divided into eight superfamilies (Flook et al., 2000) united by the reduced antennae and complete reduction of the ovipositor to only two valvular pairs. The absence of prothoracic auditory organs (when present the tympana are abdominal) is sometimes cited as a defining feature of Caelifera, but this is certainly plesiomorphic.

Orthopterans are the most "vocal" of all orders, with calling behavior playing a major role in the biology and evolution of the order. Indeed, behavioral differences in mating calls are critical for the recognition of many species that can differ very little morphologically, so it is not uncommon for new orthopteran species to be described not only by their anatomy but also by their songs. Males regularly chorus on warm evenings for females. Sound is produced either by rubbing a specialized area of the wing against a corresponding area on the other, overlapping forewing (Ensifera) or by scraping the legs against stiff edges of the forewings (Caelifera). Scrapers or files are used to create the rasping sounds (Figure 7.20), these being amplified by specialized membranes of the wings referred to as "mirrors" (Figure 7.21). Many factors can affect the sounds produced, such as the number of ridges or teeth on the files, the size and density of these teeth, the position of the mirror relative to the scraper, the size of the mirror, and the rate at which the file and scraper are rubbed. The manner of stridulation is very diverse in assorted lineages of both suborders. For example, crickets stridulate by scissoring their shortened, leathery forewings together, typically the right wing is rubbed across the left wing. Perhaps the most remarkable form of stridulation in the order does not involve the wings at all. Cylindra-chetids, a relict family of the Tridactyloidea (Caelifera), stridulate by rubbing their mandibles together, obviously independently derived from other modes of sound production. Another remarkable means of producing and altering the song is found in the gryllotalpids (Caelifera) in which individuals build cone-shaped "amphitheatres" at the opening of their subterranean tunnels, which amplify their calls.

Concomitant with sound production is, of course, the ability to hear the songs. Ensiferans typically produce longdistance, airborne sounds and detect these with tibial tympana (Figure 7.22). Some species produce substrate-borne drumming for close-range communication. For example, Stenopelmatidae were long believed to be "silent" despite the fact that they possess tibial ears; they do not sing but drum (e.g., Weissman, 2001). The tibial ears of ensiferans, when present, are located on the fore-tibia, facing forward, and their separation from one another (i.e., when the legs are spread apart) improves the ability of the insect to determine the directionality of the sound.

The pulse rate of songs is temperature-dependent, with the rate increasing with temperature. Songs are used in vari-

7.20. The microscopic file on the forewing of a Gryllus cricket, which when scraped against a small knob on the other forewing produces the familiar stridulating trill of Gryllidae. Orthopterans sing to attract mates and advertise territories, and the songs are almost always species-specific. Scanning electron micrograph.

7.20. The microscopic file on the forewing of a Gryllus cricket, which when scraped against a small knob on the other forewing produces the familiar stridulating trill of Gryllidae. Orthopterans sing to attract mates and advertise territories, and the songs are almost always species-specific. Scanning electron micrograph.

ous contexts, and most species produce entire suites of context-dependent as well as species-specific songs. "Calling songs" attract mates while "courtship songs," of low frequency (presumably to avoid drawing the attention of competing males), lure the female into copulation. Crickets and some other species also have "fighting songs," which are used for display and ritualized fighting. The diversity of orthopteran songs can be attributed to sexual selection, and

7.21. The circular, drum-like mirror is easily seen on this cricket forewing from the Early Cretaceous of Brazil. The mirror produces sound by amplifying stridulation from the file, which lies very close to the mirror. AMNH; wing length 9 mm.

some studies have documented how natural selection keeps songs from becoming too elaborate.

Males sing to females but also advertise themselves to eavesdropping parasitoids and predators. Pheromones are usually very receptor-specific, and few predators have evolved the ability to track such chemical cues, but sounds are very conspicuous. As male-male competition becomes more intense, structures of combat and display become more exaggerated, but they are kept in check by predation and par-asitoidism. For example, singing male crickets attract ormi-ine tachinid flies, a worldwide group of parasitoids that lay their larva on or near singing males. The fly larva burrows into the cricket, feeds internally, and eventually kills the host. These flies possess a unique ear that is specialized for hearing ensiferan calls. Portions of the song that are most attractive to females are also the ones most attractive to the flies (Cade,

7.22. Foretibial tympanum of a cricket, which serves as an ear drum. Scanning electron micrograph.

Gryllacrididae: Raphidophorinae

Stenopelmatidae

Gryllacrididae: Raphidophorinae

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