Caelifera

The suborder Caelifera consists of about 11,000 species in 20 families, depending on the classification followed. The phy-logeny of Caelifera has been repeatedly investigated using molecular data (e.g., Flook and Rowell, 1997, 1998; Rowell and Flook, 1998; Flook et al., 1999, 2000), while similar studies based on morphology have lagged behind. The most extreme classification of a subset of Caelifera was that of Dirsh (1975) who went so far as to break the acridomorphs into a series of separate orders! Permian families such as Per-melcanidae are stem groups to the Elcanidae (Triassic through Cretaceous), which itself is either paraphyletic or a sister group to the Caelifera despite having elongate, ensiferan-like antennae (Bethoux and Nel, 2002). The earliest definitive caeliferans are those from the Triassic, represented by several extinct families such as Locustopseidae and Locus-tavidae, which may prove to be stem groups to some of the modern superfamilies. Caelifera were diverse by the end of the Triassic and have been very significant phytophages in ecosystems ever since. Modern families are first documented in the Cretaceous, such as Eumastacidae, Tetrigidae, and Tri-dactylidae, although putative tetrigids and tridactylids have been described from the Early Jurassic. The familiar Acridi-dae is first definitively recorded from the Eocene. Lin (1980) has described a putative acridid from the Early Cretaceous of China, but this is perhaps a member of the extinct family

Locustopseidae. Some of the Tertiary records of fossil acri-dids also document gregarious associations (e.g., Arillo and Ortuno, 1997). Most caeliferans are preserved as compression fossils, but smaller species are often captured in amber, particularly nymphs (Figure 7.33).

The most diverse and familiar superfamily of caeliferans is the Acridoidea, with about 8,000 species and comprising the grasshoppers and locusts. Aside from the nominate family Acrididae the superfamily includes the Recent families Lathiceridae, Lentulidae, Ommexechidae, Pamphagidae, Pamphagodidae, Pauliniidae, Romaleidae, and Tristiridae. Lathicerids are confined to xeric regions of southern Africa, while pamphagids and pamphagodids are principally found in Africa although the latter family also ranges into the Palearctic and southwestern Asia. Tristirids are confined to the Andean region; they are cryptically colored and blend in with small stones or leaf litter. Ommexechidae are widely distributed in South America, principally in dry, sandy areas. Like ommexechids, pauliniids are also widely distributed in South America, although the two genera of the family are nocturnal, and individuals can swim through or skate across the surface of water. Pauliniids feed on aquatic vegetation and have even been employed in control programs for water hyacinth. The Lentulidae is an African family of wingless acridoids that primarily occur on bushes and oviposit into relatively dry soil. The two major families of the Acridoidea are the Romaleidae and Acrididae; the former is principally found in the Americas, while the latter is cosmopolitan in distribution. These are the grasshoppers most individuals are familiar with, although the acridids also include the infamous locusts.

Four superfamilies, the Pyrgomorphoidea, Tanaoceroidea, Pneumoroidea, and Tetrigoidea, consist of a single family each. Pyrgomorphidae is most diverse in the Old World

7.33. A grasshopper nymph (family Eumastacidae) in Miocene Dominican amber, caught while poised to leap. Caeliferans are rare in amber because most of them are ground dwelling; they can usually extract themselves from the sticky resin using powerful hind legs. Morone Collection; 7 mm. Photo: R. Larimer.

7.33. A grasshopper nymph (family Eumastacidae) in Miocene Dominican amber, caught while poised to leap. Caeliferans are rare in amber because most of them are ground dwelling; they can usually extract themselves from the sticky resin using powerful hind legs. Morone Collection; 7 mm. Photo: R. Larimer.

tropics, particularly in the afrotropics and Madagascar. The pyrgomorphids are represented in the Western Hemisphere only in tropical Mexico. Some pyrgomorphids are toxic, even deadly, and these generally have very aposematic coloration. Tanaocerids comprise only a few species of nocturnal caelif-erans occurring in the deserts of Mexico and western North America. Pneumoridae contains about 20 species confined to sub-Saharan Africa. The family Tetrigidae is sometimes broken into a series of families. Unlike the aforementioned families, the tetrigids are moderately diverse with about 1,000 species distributed throughout the world and include the pygmy grasshoppers. Tetrigids are generally small (1 cm or less in length) and are very cryptic among the brown leaves of the forest floor.

The families Eumastacidae and Proscopiidae are the only members of the superfamily Eumastacoidea. Both families have long, angular heads and tend to be wingless, the latter exclusively so. The South American proscopiids are commonly called the false stick insects owing to their cryptic, sticklike body structure, and they are often confused with species of the Phasmatodea. Eumastacids are distributed in most areas around the world.

The superfamily Trigonopterygoidea consists of two enigmatic families, the Asian Trigonopterygidae and the Mexican Xyronotidae, the latter family formerly included in the Tanaoceridae. Neither family is very diverse, the

7.34. Pygmy mole cricket (Tridactylidae) from the Early Cretaceous of Brazil. AMNH; length 9 mm.

xyronotids in particular accounting for only two species in a single genus.

The superfamily Tridactyloidea contains three families, the closely related Tridactylidae and Rhipipterygidae and the relict Cylindrachetidae. These insects superficially resemble true crickets and mole crickets, and they also tend to be small and frequently gregarious. The tridactylids and rhipiptery-gids are most closely related, both occurring in the tropics or subtropics except for a few tridactylids that extend into temperate habitats. The family Cylindrachetidae consists of nine peculiar species commonly known as sand gropers. Cylindra-chetids are confined to the Southern Hemisphere, living in subterranean galleries in southern South America (Patagonia), Australia, and New Guinea. These insects are extremely reduced, having minute eyes, no vestiges of wings, and a soft, fleshy abdomen (Figure 14.31). The mid and hind legs are very short, and the forelegs are remarkably convergent with those of gryllotalpids. Because they do not live above ground, their dispersal ability must be very limited. That fact, and their disjunct austral distribution, suggests that they may have been affected by the drifting of gondwanan continents in the Cretaceous, which is an age that agrees with that of their close relatives, the tridactylids and rhipipterygids (Figure 7.34).

PHASMATODEA2: THE STICK AND LEAF INSECTS

Like many Orthoptera, the stick and leaf insects are remarkable mimics of the stems, twigs, and leaves (Figures 7.35 to 7.37) on which they feed. Some species are very large; in fact, the longest extant insect is a stick insect, Pharnacia kirbyi from Borneo, which can be up to 555 mm (22 inches) in length. The order has more than 3,000 species distributed in temperate and tropical habitats. Bedford (1978), Mazzini and Scali (1987), Brock (1999), and Bradler (2003) have most recently summarized the available biological information on the order. Phasmatodean monophyly is clear owing to the unique development of anterior dorsolateral defensive glands on the prothorax, which provides one of their few means of defense, but can be very effective. Additionally, males of Phasmatodea have a vomer, a sclerite of the tenth

2 Phasmida Versus Phasmatodea. Much confusion surrounds the formation of scientific names, which is not surprising. Most authors are not familiar with the intricacies of Greek and Latin. These two names naturally originate from phasma (Greek, meaning "spirit"), which is a neuter, third declension noun with an augmented stem such that its combining form is actually phasmatos. This is why when family-group names are formed from such words, the family name is slightly different from the genus upon which it was based (e.g., Phasma forms Phasmatidae). Therefore, the correct formation of any familial or ordinal name from Phasma results in Phasmatida or Phasmatodea. The alternative names of Phasmida and Phasmodea are improperly formed in Greek.

7.35. A large living species of walking stick, Eurycnema cercata from Australia (order Phasmatodea), shown here life size. The longest insect is Pharnacia kirbyi from Borneo, which can reach lengths up to 55 cm (22 in.). Body length 20 cm.

sternum that permits males to clasp the female during copulation (Sinety, 1901; Pantel, 1915; Snodgrass, 1937) but that has only recently been established as part of the stick-insect groundplan (Bradler, 1999; Tilgner et al., 1999). Other, principally internal, features of the order are discussed by

7.36. Representative living stick insects. Not all Phasmatodea are sticklike. To the same scale.

Kristensen (1975, 1991) and Tilgner et al. (1999). Lastly, the egg of phasmatodeans have an operculum, a lidlike section of the oocyte, and this trait, in combination with a unique structure of the micropyle (Sellick, 1998), supports the order's monophyly.

Aptery occurs throughout the order, but in all species that retain forewings these are relatively reduced. The forewings,

7.37. A walking stick moving across a log in an Ecuadorian forest. Most phasmatodeans live amongst the vegetation they feed on, remaining motionless or even swaying with branches to better camouflage themselves. Photo: R. Swanson.

when present, are tegminous and abbreviated. The hind wings are often altered so as to either fold tightly against the long, thin body, or modified to resemble leaves, like the forewings in such species. Cryptic coloration, elongation of the body and legs, or, alternatively, broadening and flattening of the body to resemble leaves are other important adaptations. Stick insects also "sway," or gently rock backward and foreward, resembling rustling leaves or branches in a breeze. Phasmatodeans also protect themselves by feeding at night and remaining virtually motionless during the day. If disturbed or attacked, most stick insects become cataleptic, falling from their perch and laying motionless for hours. Some species will attempt to stand their ground, armed with sharp, thorny spines, or emitting noxious secretions, even regurgitating their gut contents. The secretions are sprayed from exocrine glands opening at the anterolateral corners of the prothorax, and at least some include chemicals such as quinoline and can cause blindness, although the chemistry of most are unknown.

Stick insects apparently take little care in egg deposition. The ovipositor is reduced relative to other orthopterids, and female phasmatodeans tend to scatter eggs from upon high. Some species deposit eggs within the soil or cement them to plants, but typically, without changing position, a stick insect will fling eggs from the tip of the abdomen so that they fall amidst leaf litter. To protect eggs, crypsis in Phasmatodea extends even to this early stage, with a bewildering array of egg modifications across the order (Figure 7.38). Many eggs resemble seeds and, like seeds, may not hatch for years and are resistant to various forms of damage. A capitulum is developed in some lineages that flings their eggs to the ground. This knoblike process on the anterior end of the egg resembles the elaiosomes of some seeds. Elaiosomes are lipid-rich processes of seeds that attract ants, who then col lect and disperse the seeds. Amazingly, ants readily collect these eggs and in removing them from the leaf litter to their nests, young stick insects have the protective confines of the subterranean colony and thereby avoid parasitism and predation. Eventually, the egg opens from the operculum and the nymph emerges. It resembles the adult except in the smaller number of antennal segments and rudimentary wings and genitalia. A study of crypsis from a phylogenetic perspective in adult and immature Phasmatodea will be of great significance, and already egg morphology is proving important for Phasmatodea classification (Sellick, 1997a,b,c, 1998).

Phylogenetic work within Phasmatodea has been essentially lacking, and the classification has changed little since Gunther's (1953) treatment of the order. Bradley and Galil (1977) and Kevan (1977, 1982) had dramatically different classifications, neither of which are entirely well founded. Kristensen (1975) highlighted the segregation of the relict genus Timema (Timematidae) from other Phasmatodea, and the importance of this group is recognized today by its placement into a separate suborder, Timematodea, versus all other families (i.e., the Euphasmatodea). The 21 species of Timema occur in western North America, principally in California (Vickery, 1993; Sandoval and Vickery, 1996, 1998; Vickery and Sandoval, 1997, 1998, 1999, 2001) (Figure 7.39), but were assigned to the paraphyletic "Areolatae" of earlier classifications (e.g., Bradley and Galil, 1977). Timematidae is one of the only groups of stick insects to have been studied phylogenet-ically, principally to investigate the evolution of parthenogenesis, which appears to have arisen at least five times within the family (Sandoval et al., 1998; Crespi and Sandoval, 2000; Law and Crespi, 2002) (many other stick insects are also parthenogenetic). Timema, like all organisms, is a mosaic of derived and primitive traits, and its monophyly is supported by three-segmented tarsi, development of a mesal lobe on the right cercus, and egg-laying behavior, in which females ingest soil and then coat the eggs with this material (Tilgner et al., 1999). The genus is excluded from Euphasmatodea by the primitive features of a molar lobe on the mandible, separation of the prothoracic ana- and coxopleurites, and retention of prothoracic sternal apophyses (Kristensen, 1975). Unfortunately, there is no fossil record for Timematodea.

The grouping within Euphasmatodea of two infraorders (traditionally considered suborders), namely the Areolatae and Anareolatae, is unnatural, and neither group is mono-phyletic (Bradler, 1999, 2003). These groups were established on the presence or absence of the area apicalis, a sharply defined region near the apex of the mid- and hind tibiae (Redtenbacher, 1906; Bradley and Galil, 1977). The presence of this structure in Timema suggests that it is primitive for the order and thus the Areolatae is paraphyletic. In fact, some Areolatae and some Anareolatae share the derived feature of a gula; consequently, it is likely that the area apicalis was

Phibalosoma Haaniella Ctenomorphodes

7.38. Photomicrographs of representative stick insect eggs. The diverse and elaborate eggs are dropped from the plant and sometimes brought back to the nests of seed-gathering ants, where they are protected. Specimens: University of Georgia.

Phibalosoma Haaniella Ctenomorphodes

7.38. Photomicrographs of representative stick insect eggs. The diverse and elaborate eggs are dropped from the plant and sometimes brought back to the nests of seed-gathering ants, where they are protected. Specimens: University of Georgia.

reduced twice within the order, rendering Anareolatae poly-phyletic (Bradler, 1999, 2003). The most recent work on the phylogeny of Euphasmatodea arrived at a novel set of relationships based on molecular data, suggesting that, under the most parsimonious reconstruction, wings, once lost, were reacquired several times independently (Whiting et al., 2003). This is not to say that wings in many Phasmatodea are novel structures, unrelated to wings in other Pterygota. Indeed, the basic structure of the wings is identical to other lineages, complete with the typical venation, etc. Instead, it appears that the genes controlling expression of the wings were suppressed early in stick-insect evolution, becoming reactivated several times independently throughout the order's history. However, Trueman et al. (2004) noted that since wings are commonly lost in diverse insect lineages, this better accounts for phasmatodean wing evolution, rather than hypothesizing an ancestral loss and multiple reacquisitions. Indeed, stem-group Phasmatodea were fully winged (Willmann, 2003), lending support to the multiple-loss hypothesis. Without a fossil record for Timematodea and a more extensive record for basal Euphasmatodea, however, the paleontological data cannot presently resolve the debate (see following discussion), so additional paleontological study is needed.

Sharov (1968), Carpenter (1992), Rasnitsyn and Quicke (2002), and Willmann (2003) considered the stick insects as having an extensive geological record extending back to the Permian or Triassic (Figure 7.18). In sharp contrast, Tilgner

7.39. Timema, the most basal lineage of Phasmatodea. The genus occurs in western North America. Photo: C. Sandoval.

(2000) concluded that these fossils possessed no defining features of Phasmatodea. Although the development of subparallel veins in the forewing has been considered a phasma-todean trait (e.g., Rasnitsyn and Quicke, 2002), there are both Ensifera (e.g., Proparagryllacrididae) and Caelifera that also possess such characters, and putative stick insects such as Xiphopterum approximate caeliferan families such as Locustopseidae. The Mesozoic fossils are perhaps stem-group Phasmatodea as demonstrated by Willmann (2003). Tertiary stick insects are rare and only a few species are documented from Baltic and Dominican ambers (Figures 7.40, 7.41).

As discussed before, eggs of stick insects are diverse in structure and are very hardy; some eggs even occur in the fossil record. Definitive eggs of Euphasmatodea are known from as old as the mid-Cretaceous of Myanmar (Rasnitsyn and Ross, 2000) as well as from Eocene deposits of North America (Sellick, 1995) and in Dominican amber (Tilgner, 2000).

TITANOPTERA: THE TITANIC CRAWLERS

Among the most impressive Orthopterida are the giant titanopterans (Figure 7.42). These insects, known only from the Triassic of Australia and central Asia (Tillyard, 1925; Riek, 1954; Sharov, 1968; Jell and Lambkin, 1993), could reach 400 mm (15.75 inches) in wingspan (Sharov, 1968). Although the order was first recognized under the name Mesoti-

7.40. A nymph of the Eocene phasmatodean Pseudoperla in Baltic amber. AMNH; body length 13 mm.

tanoptera by Crampton (1928), it was not accepted by authors until the more extensive monograph of Sharov (1968). Unlike Orthoptera, titanopterans had five-segmented tarsi, cursorial (running) legs not capable of jumping, and wings that were held flat over the abdomen during rest. The forelegs appeared to be raptorial, being ventrally armed with stout spines on the femora and tibiae. The forewings of many species possessed large stridulatory structures, so these were clearly very vocal animals. Because the wings were held over the abdomen during rest, sound was perhaps produced by rubbing the stridulatory files/scrapers of the tegminous forewings together, typical of modern Ensifera. Given the preserved details of the stridulatory structures, it is likely that

7.41. A Miocene phasmatid in amber from the Dominican Republic. Morone Collection; length 48 mm. Photo: R. Larimer.

7.42. Wing of Clatrotitan andersoni, from the Triassic of Australia. Titanopterans were giant, raptorial orthopterids from the Triassic. Large stridulatory structures on the patterned forewings show that they were vocal like their orthopteran relatives; in fact, they were probably the baritones of Mesozoic insects. Australian Museum (AM) F.36274; length 139 mm.

7.42. Wing of Clatrotitan andersoni, from the Triassic of Australia. Titanopterans were giant, raptorial orthopterids from the Triassic. Large stridulatory structures on the patterned forewings show that they were vocal like their orthopteran relatives; in fact, they were probably the baritones of Mesozoic insects. Australian Museum (AM) F.36274; length 139 mm.

these would have had relatively deep calls, probably a resonant call like a bullfrog. The pronotum extended laterally over the pleura and hypognathous head capsule, which are features shared with Orthoptera, and it is possible that, like other orthopterid orders, Titanoptera is derived from within a paraphyletic assemblage of Paleozoic orthopterids, their closest relatives being the spectacular Permian Geraridae (Figure 7.43) (Gorokhov, 2001). Certainly much remains to be discovered concerning these giants. Although presently known only from deposits in present-day Australia and Asia, the consolidation of continents during the Triassic into Pangea implies that they will likely be discovered in strata of similar age from Africa, North America, and South America. The absence of Titanoptera from Jurassic deposits in Europe and Eurasia indicates that these fascinating insects were narrowly restricted to the Triassic, which may be a consequence of Titanoptera being a crown group to the Paleozoic Geraridae.

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