. Common Illinois insects : and why they are interesting. Insects -- Illinois. Insects are the most numerous of the invertebrates, the animals without a backbone. Insects belong to a branch of animals (Phylum) called Arthropods. This phylum contains, along with insects, the cray- fishes, crabs, scorpions, spiders and thousand legged worms. These are placed in separate Classes of which the largest is Class Insecta. All the orders and families of insects have evolved from one an- other in many directions. Those living in the world today have descended from a line of ancestors that extends backwa
. Common Illinois insects : and why they are interesting. Insects -- Illinois. Insects are the most numerous of the invertebrates, the animals without a backbone. Insects belong to a branch of animals (Phylum) called Arthropods. This phylum contains, along with insects, the cray- fishes, crabs, scorpions, spiders and thousand legged worms. These are placed in separate Classes of which the largest is Class Insecta. All the orders and families of insects have evolved from one an- other in many directions. Those living in the world today have descended from a line of ancestors that extends backward in time over 300 million years. In Coal - Age deposits of Illinois and in other rock formations "elsewhere many ancestral forms of present day insects have been dis- covered as fossils. With the help of such petrified remains and through a close study of living insects it has been possible for scientists to determine the general trend of insect evolution. The living varieties may be grouped together in such a way as to demonstrate something of the various steps througJi which the main line of progress in de- velopment has been made. The most primitive insects are small and wingless and have no transformations from larva to adult (metamor- phosis) as described in a later section. A common example of this insect type is the Silverfish or Firebrat (called Silver fish because of the shiny fish-like scales, Firebrat because of its frequenting of fire places.) Their. Nest of Mount-builder Ant. {Formica exsectoidcs) The highest level of care for young and most complex social behavior among invertebrates is attained by ants, bees and wasps. Order Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Wright, A. Gilbert (Arthur Gilbert), 1909-. Springfield, Il. : Dept. of Registration and Education
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