See also:HISTORY The
See also:classification just given has been
See also:drawn up with reference to existing
See also:insects, but the
See also:great majority of the
See also:extinct forms that have been discovered can be referred with some confidence, to the same orders, and in many cases to
See also:recent families . The Hexapoda, being aerial, terrestrial and fresh-
See also:water animals, are but occasionally preserved in stratified rocks, and our know-ledge of extinct members of the class is therefore fragmentary, while the description, as insects, of various obscure fossils, which are perhaps not even Arthropods, has not tended to the
See also:advancement of this branch of zoology . Nevertheless, much progress has been made . Several
See also:Silurian fossils have been identified as insects, including a Thysanuran from
See also:America. but upon these considerable doubt has been
See also:cast . The Devonian rocks of
See also:Canada (New
See also:Brunswick) have yielded several fossils which are undoubtedly wings of Hexapods . These have been described by S . H . Scudder, and include gigantic forms related to the Ephemeroptera . In the Carboniferous strata (
See also:measures) remains of Hexapods become numerous and quite indisputable . Many
See also:European forms of this age have been described by C . Brongniart, and
See also:American by S . H .
Scudder . The latter has established, for all the Palaeozoic insects, an
See also:order Palaeodictyoptera, there being a closer similarity between the fore-wings and the
See also:hind-wings than is to be seen in most living orders of Hexapoda, while
See also:affinities are shown to several of these orders—notably the Orthoptera, Ephemeroptera, Odonata and Hemiptera . It is probable that many of these Carboniferous insects might be referred to the Isoptera, while others would fall into the existing orders to which they are allied, with some modification of our
See also:present diagnoses . Of
See also:interest are cockroach-like forms, with two pairs of similar membranous wings and a long ovipositor, and gigantic insects allied to the Odonata, that measured 2 ft. across the outspread .wings . A remark-able fossil from the Scottish Coal-measures (Lithomantis) had apparently small wing-like structures on the prothorax, and in allied genera small veined outgrowths—like tracheal gills—occurred on the abdominal segments . To the
See also:period belongs a remarkable genus Eugereon, that combines hemipteroid jaws with orthopteroid wing-neuration . With the
See also:dawn of the Mesozoic epoch we reach Hexapods that can be. unhesitatingly referred to existing orders . Froth the Trias of
See also:Colorado, Scudder has described cockroaches intermediate between their Carboniferous precursors and their present-
See also:day descendants, while the existence of endopterygotous Hexapods is shown by the remains of
See also:Coleoptera of several families . In the
See also:Jurassic rocks are found Ephemeroptera and Odonata, as well as Hemiptera, referable to existing families, some representatives of which had already appeared in the
See also:oldest of the Jurassic ages—the
See also:Lias . To the Lias also can be traced back the Neuroptera, the Trichoptera, the orthorrhaphous
See also:Diptera and, according to the determination of certain obscure fossils, also the Hymenoptera (ants) . The Lithographic
See also:stone of Kimmeridgian age, at Solenhofen in
See also:Bavaria, is especially
See also:rich in
See also:insect remains, cyclorrhaphous Diptera appearing here for the first
See also:time . In
See also:Tertiary times the higher Diptera, besides Lepidoptera and Hymenoptera, referable to existing families, become fairly abundant: Numerous fossil insects preserved in the
See also:amber of the Baltic Oligocene have been described by G .
L . Mayr and others, while Scudder has studied the rich Oligocene faunas of Colorado (Florissant) and
See also:Wyoming (
See also:River) . The Oeningen beds of Baden, of
See also:Miocene age, have also yielded an extensive insect
See also:fauna, described fifty years ago by O . Heer . Further details of the geological history of the Hexapoda will be found in the special articles on the various orders . Fragmentary as the records are, they show that the Exopterygota preceded the Endopterygota in the
See also:evolution of the class, and that among the Endopterygota those orders in which the greatest difference exists between imago and larva—the Lepidoptera, Diptera and Hymenoptera—were the latest to take their rise .
GEOID (from Gr. yij, the earth)
GEOLOGY (from Gr. yp7, the earth, and Abyor, scienc...
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