Plecopterida

Three disparate relatives within the Polyneoptera are the very generalized stoneflies and the highly specialized webspinners and zorapterans. The placement of these three orders in the grander scheme of the insects has been troublesome for many years. The crux of the problem is that each is without clear affinity to any other order and each is a recent remnant of an otherwise ancient lineage. As alluded to before, it is exactly for such groups that paleontological data are hypothesized to be...

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Grylloblattodea

Reconstruction of Gerarus danielsi (Geraridae), from the Late Carboniferous of Mazon Creek, Illinois. Gerarids were Paleozoic orthopterids and a stem group to the Titanoptera. Redrawn from Burnham (1983). 7.44. The caloneurodeans, such as Paleuthygramma tenuicornis (Paleuthygrammatidae) from the Permian of Russia, were enigmatic relatives of early Orthoptera and Phasmatodea that became extinct probably at the end of the Permian. Length 24 mm redrawn from Carpenter (1992). 7.44. The...

Brief History Of Work

The history of entomology, although an engaging topic, has been more thoroughly covered elsewhere (Essig, 1931 Smith, 1973). The following is an account of those post-Darwinian authors who have contributed most significantly to our knowledge of insect phylogeny and the fossil record. Even though early authors did consider the various affinities among major groups, like the quinarians of the early nineteenth century, it was not until Darwin provided his theory of evolution that systematists...

Fff

A mayfly naiad (nymph) of Hexagenia (above), which has tusks protruding from its mandibles that are used for burrowing. A more typical mayfly naiad is below. Like the adults, immature mayflies have three terminal filaments, a groundplan feature of insects. Length 23 mm (above), 8 mm (below). number into the tens of millions of individuals and form clouds of dense swarms. Within a day of swarming, their corpses can pile up on roadways or in towns where they had been attracted by lights. In...

Devonian 414358 mya

The earliest evidence of hexapods, the group of arthropods to which insects belong, comes from a few fragmentary remains of apterygote lineages from the Devonian. Although plants had long since colonized the land, this invasion was slow, and in the Early Devonian most plants were confined to moist, lowland environments or still consisted of mats growing on the surface or edges of pools. These primitive vascular plants were not complex and consisted of relatively simple shoots that generally...

Trace Fossils Ichnofossils

Some groups of insects don't readily fossilize, particularly soft-bodied ones, but remains of their activities persist. These largely involve structures on plants, like larval feeding mines on leaves, chew and puncture marks on leaves and stems, galls, and galleries in wood. Plants are abundant in the terrestrial fossil record, and because insects are the predominant group of herbivores, these trace fossils provide a unique and direct record of past plant-insect associations and remarkable...

What Is Pterthorax

A beautiful adult male mayfly in mid-Cretaceous amber from New Jersey. AMNH NJ1018 body length 6 mm. 6.14. A beautiful adult male mayfly in mid-Cretaceous amber from New Jersey. AMNH NJ1018 body length 6 mm. 6.15. A mayfly, family Baetidae, in Miocene amber from the Dominican Republic. Many mayflies have very small hind wings, and in baetids the hind wings are often extremely reduced. Morone Collection M3351. Photo R. Larimer. 6.15. A mayfly, family Baetidae, in Miocene amber from the...

Paleozoic Herbivory

The Palaeodictyopterida were the first major group of herbivorous insects. We tend to think of the impact of herbivorous orthopterans, phytophagan beetles, plant bugs, and caterpillars on modern ecosystems, but during the Paleozoic the palaeodictyopterids were among the primary herbivores. They probably caused much of the plant-tissue damage during the Permian and Late Carboniferous (perhaps even into the Early Carboniferous, although body fossils are lacking), and in fact feeding scars can be...

Triassic 247208 mya

The Triassic was dramatically different than the Permian, with a mean global temperature (mgt) of near 22 C, compared Tropical summerwet cool-cold temperate Tropical summerwet cool-cold temperate 2.47. Continental configurations and climate during the Permian. to the 12-15 C mgt in the first half of the Permian. No ice occurred at either pole, and floras changed from archaic lycopsids, ferns, cordaites, and pteridosperms, to radiations of cycads, ginkgos, conifers, and the angiosperm-like...

Drosophila

-William Morton Wheeler, on Drosophila melanogaster Drosophila fruitflies may not have the behavioral repertoire of ants that so fascinated the famous entomologist W. M. Wheeler, but Drosophila has revolutionized biology more than any other organism. Contrary to popular belief, Drosophila does not naturally live in little vials. There are approximately 1,000 species in the genus, which breed in a great variety of plants and other substrates. Some species are highly polyphagous and have followed...

Introduction

Evolution begets diversity, and insects are the most diverse organisms in the history of life, so insects should provide profound insight into evolution. By most measures of evolutionary success, insects are unmatched the longevity of their lineage, their species numbers, the diversity of their adaptations, their biomass, and their ecological impact. The challenge is to reconstruct that existence and explain the unprecedented success of insects, knowing that just the veneer of a 400 my sphere...

The Thorax

The thorax is the middle tagma of insects and is the main unit for locomotion because it bears the legs and, in pterygotes, the wings. The thorax primitively consists of three metameres although the first abdominal segment is closely associated with the thorax in Pterygota and is completely fused to it in the Apocrita (Hymenoptera). Each thoracic segment has one pair of legs. Anteriorly, there is a membranous region where the head attaches to the thorax. This is the cervix (Latin, meaning...

Insect Fossilization

Too often insect fossils are thought to be merely impressions of wings scattered in slabs of rock. Wings are indeed a common insect fossil. They do not readily decay or digest, which is why birds and spiders typically leave the wings after devouring the rest of an insect. Fortunately, wing veins are also a veritable road map to the identification and phylogeny of insects, much the way crowns and pits are on the teeth of mammals. Most isolated insect wings, in fact, are readily identifiable to...

Charcoalified Fusainized Remains

Recently discovered are three-dimensional insect remains, buried in Cretaceous clays and lignitic peats amidst abundant fossil plant material (Grimaldi et al., 2000a). The remains were found by paleobotanists prospecting for flowers, cones, and other structures that had been fusainized, or rendered to charcoal by ancient forest fires (e.g., Friis et al., 2.14. A group of pyritized larvae, presumably in a gall or wood cavity, from the Eocene London Clay. NHM In. 64736 diameter of gall 11 mm....

Ensifera

Schizodactylidae

The Ensifera consists of about 10,000 species in 10 families. The phylogeny of Ensifera has been most recently investigated by Gwynne (1995) and Desutter-Grandcolas (2003). Among ensiferans are some clear relicts, such as members of the Stenopelmatoidea and Hagloidea. As alluded to earlier, Ensifera is the older of the two suborders, with putative members recorded from the very end of the Permian (Bethoux et al., 2002), and the lineage was certainly established during the Triassic. Numerous...

Pleistocene and Holocene Traps

The accumulation of insects in sediments that formed during the Quaternary (1.7 mya to present) provides unique insight on climate change and the duration of species, a subject treated thoroughly by Elias (1994). Most Quaternary remains occur in peats from mature successional stages of bogs, which are the edges. Here, the thickly sclerotized, durable elytra, pronota, and heads of beetles predominate. Fortunately, the gross structure and microsculpturing of beetle sclerites allow detailed...

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...

Types Of Preservation

Compressions and Impressions are the most extensive types of insect fossils, occurring in rocks from the Carboniferous to Recent. Impressions are like a cast or mold of a fossil insect, showing its form and even some relief (like pleating in the wings) but usually little or no color from the cuticle (Figure 2.2). Compressions preserve remains of the cuticle, so color also distinguishes structures (Figure 2.3). In exceptional situations microscopic features such as microtrichia on sclerites and...

Costal

A generalized wing, indicating major vein systems and the terminology used in this book. 4.5. A generalized wing, indicating major vein systems and the terminology used in this book. on various modifications of the Comstock-Needham system (e.g., Comstock and Needham, 1898, 1899 Kukalova-Peck, 1991). Here, we adopted the system that is most similar to that espoused by Wootton (1979) (Figure 4.5). Major longitudinal veins typically have major branches, each given names, and are indicated by...

The Invasion Of Land

Insects are principally terrestrial organisms. Indeed, despite frequent colonization of freshwaters by mayflies, dragonflies, diving beetles, predatory water bugs, various midges, and other groups, they are all terrestrial organisms by original design. The transition to land took place in the ancestor of insects and their closest relatives, the Entognatha. The freshwater life-histories of immature mayflies (Ephemeroptera), dragonflies and damselflies (Odonata), and many other insects evolved...

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Protorthoptera

Kemperala (Paoliidae) from the mid-Carboniferous of Germany. Paoliids, which occurred from the mid- to Late Carboniferous, were among the earliest known winged insects, but they also folded their wings over their backs and may have been the earliest neopterans. Photo C. Brauckmann. difficult to place into or near any one of these lineages. Even though our understanding of relationships among hexapods is congealing, the ancient origins and relationships among early polyneopterans has been...

Cheliceriformes

Schizomida Amber Dunlop

Basal cheliceriformes such as Aglaspidida and Chasmatasp-ida show an intuitive primitive similarity to the Trilobites but also resemble the early chelicerates such as xiphosurans (horseshoe crabs). Along with the marellomorphs, these lineages were at one time considered as a group, called Trilo-bitomorpha, that has since been recognized to be artificial (e.g., Wills et al., 1998). Little is known of the extinct Aglaspi-dida and Chasmataspida and the best understood lineage is that of the...

Arthropods and the Origin of Insects

Multicellular life arose in the Precambrian Period. While many animal phyla appear to have originated near the end of the Precambrian (e.g., putative annelids), the first diverse assemblages of animals is not known until the Cambrian, the so-called Cambrian Explosion (Conway Morris, 1979, 1989, 1993, 1998, 2000, 2003). We recognize these lineages as phyla because of the dramatic and fundamental differences in body organization (i.e., each phylum represents a basic groundplan or bauplan for...

Roadmap To The Phylogeny Of Insects

The remainder of this book concerns itself with the major groups of insects, with accounts of their relationships, biology, and evolution. We have attempted to outline the relationships among the Recent and extinct insect orders as we believe are best supported by current morphological, molecular, and paleontological evidence. Figure 4.24 is a phylogeny of orders and the principal superordinal groups employed throughout this volume, with the classification summarized in Table 4.1. 4.23. Niels...

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Genitalia Andreniformis

Relationships among species of Recent honey bees, genus Apis, showing important variations in tarsomeres and male genitalia. Relationships from Engel and Schultz (1997). entirety of their ranges, distinct from regional morphotypes or ethotypes, and that may be reproductively isolated at fine geographical scales Perhaps the most dramatic development of variation is seen in the Cape honey bee, Apis mellifera capensis. This subspecies is facultatively parthenogenetic and a social parasite on...

Info

Diversity Carabid Beetles

From multiple individuals of this tree Erwin found, among hundreds of beetle species, 163 species occurring only on this tree, presumably restricted to it. By his calculations, because there are approximately 50,000 species of tropical trees, the number of beetle species living in tropical forest canopies would be 8,150,000. Because beetles comprise approximately 40 of all terrestrial arthropods, the number of tropical forest arthropods is likely to be 20 million...

Mandibulata Mandibulata Versus Schizoramia

The placement of Crustaceomorpha has been of considerable contention, with the primary schism lying between paleontologists who believe the group to be sister to the Arachnomorpha, and the neontologists who support a mandibulate arthropod group (i.e., Crustacea allied to the Hexapoda and Myriapoda) (Figure 3.1). In most recent analyses, albeit ones that did not include several critical fossils, the Mandibulata is supported as monophyletic (e.g., Scholtz et al., 1998 Bitsch, 2001 Giribet et al.,...

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...

Earliestlnsects

Thysanura Representative

Bristletails, or Archaeognatha ( Microcoryphia), are the most primitive of living insects, having persisted since at least the mid-Devonian. These cryptic, somewhat cylindrical insects occur under loose bark or stones (Figure 5.1). Except for a rare few, bristletails are nocturnal and typically hide in crevices during the day. About 500 species are known worldwide and live in diverse habitats, including elevations as high as 4,800 meters (15,749 feet) in the Himalayas. The typical diet of...

Nearctic and Palearctic

The Paleocene is a very poorly known period in the geological record of insects. Though major lineages of insects, like families, were largely unaffected by the mass extinctions at the end of the Cretaceous, we have very few details about how insect faunas responded to this cataclysm (see, for example, Labandeira et al., 2002). North America was in the direct wake of the ejecta from the giant meteorite that fell at Chixculub, Mexico 65 mya, so Paleocene insect faunas from...

Dicliptera

This group includes the Diathemoptera and Permoth-emistida however, it was referred to as Martynov's Archodonata in Kluge's (2000) treatment of palaeopterous insects. We prefer the more descriptive name Dicliptera, in reference to the vestigial or absent hind wings. Dicliptera are notable among palaeodictyopterids for an absence of paranotal lobes and archedictyon, presence of a distinct pterostigma (as a heavily infuscated region, and not formed of fused or expanded veins as in Hymenoptera),...

Megasecoptera

Megasecoptera in the sense used by Carpenter (1992) are possibly paraphyletic, with the Eubleptoptera being more primitive. The order is difficult to define as distinct from the Palaeodictyoptera when the Eubleptoptera is included, and Carpenter (1992) suggested that Megasecoptera might be merged with Palaeodictyoptera. Such a decision, however, would only further cloud relationships within this lineage, and we have, conservatively, retained the principal lineages pending phylogenetic study....

The Head

Occipital Sulcus Beetles

Cephalization has occurred in all arthropods, where one tagma is always present at the anterior end of the body and minimally has the functions of food intake, sensory perception, and neural integration and command. Most of the head is occupied by musculature, and the brain takes up little space. The details of cephalization in the different arthropod lineages, however, differ and can be used to define major arthropod lineages. For any given lineage, we can ask, How many segments are present in...

Atelocerata Versus Pancrustacea

Within the Mandibulata we are faced with a similar problem concerning the relationships of lineages. As discussed, the mandibulate arthropods include the Crustacea, the Myriapoda, and the Hexapoda. Traditionally, myriapods and hexapods have been considered sister groups (e.g., Snod-grass, 1938) and together called either Tracheata or, more widely, Atelocerata (Figure 3.22). Familiar traits defining the Atelocerata include the loss of the second antennal pair, presence of a tentorium (internal...

When Is It a Fossil

Well-preserved remains of living insect species in the Quaternary, and even lifelike preservation of extinct species in amber millions of years old, forces the question as to when remains are considered fossils. After one million years After the original remains have been replaced by minerals For some, a fossil is the remains of a species that has become 2.36. A botfly puparium (Cobboldia) from the stomach of a mammoth found in Siberia. Paleontological Institute Moscow (PIN) Q-TA-1 1 length 19...

Rhyniognatha

Rhyniognatha Hirsti

Rhyniella, the collembolan in Early Devonian Rhynie chert, has long been heralded as the oldest hexapod, while fragmentary remains from the same chert had been mostly forgotten. In the original paper announcing the discovery of Rhyniella, Hirst and Maulik (1926) also reported a pair of mandibles preserved with largely unidentifiable tissues surrounding them (Figure 5.8). Later, Tillyard (1928b) formally described the mandibular elements and named them, Rhyniognatha hirsti. Tillyard was the...

Marellomorpha The Lace Crabs

The extinct subphylum Marellomorpha consists of several enigmatic marine fossils from the Cambrian to Devonian, the most famous of which is Marella (the lace crab) from the Burgess Shale (Wolcott, 1912), and is perhaps the most common nontrilobite arthropod in these deposits. Other genera include Mimetaster and Vachonisia. The lineage is supported as monophyletic based on four traits (St rmer and Bergstr m, 1976 Wills et al., 1998) number of head appendages, large number of trunk somites,...

Myriapoda

The Myriapoda has not been widely supported as a natural group (although see Zrzavy et al., 1998b). Indeed, several studies indicate that the centipedes (Chilopoda) and sym-phylans are basal (although not themselves related), while the Dignatha (Pauropoda and Diplopoda millipedes ) comprise a sister group to the Hexapoda (e.g., Wheeler, 1998 Kraus, 2001). The symphylans are sometimes classified with the Dignatha into a larger group called the Progoneata. Other views on the phylogeny of...

Dicondylia

The traditional taxon Thysanura, or Apterygota, has been recognized as an unnatural group for decades because silverfish (Zygentoma) are more closely related to the winged insects (Pterygota) than to the bristletails (e.g., Snodgrass, 1935). In his monumental work on the phylogeny and classification of insects, Hennig (1953, 1969, 1981) proposed the name Dicondylia for the group uniting the silverfish with the winged insects. Recent molecular studies have also supported the Dicondylia as a...

Permian 290248 mya

The world of the Permian saw a steady decline in the intensely hyperoxic and tropical global climate of the Carboniferous. Even though the opening of this period was similar to that of the Carboniferous world, its close would be marked by the most traumatic cataclysm earth ever experienced (Kaiho et al., 2001). Like the Carboniferous, relatively few deposits provide significant glimpses into the insect fauna at this time. In fact, there are five principal deposits -two from the Early Permian,...

Geroptera

The Geroptera comprise a single family of primitive odonatopteroids, Eugeropteridae, from the early Late Carboniferous (Early Bashkirian Namurian) of Argentina (Riek and Kukalova-Peck, 1984). While a quick glance at the primitive wings of geropterans reveals little affinity to anything one might identify as a dragonfly or damselfly, finer study indicates a shared, albeit distant, ancestry between the groups (as noted earlier). Superficially, the order more closely resembles the...