Insect general information is spread over a number of pages. This page is divided into 3 sections, 1. A list of the insect orders with a link to the main page for that order, 2. A list of topics relating to insects in general, amid 3, A very brief overview of the insects. Insects are in the Phylum Uniramia, and I've included links to pages in this phylum too.
List of general insect topics
Smith, L. (2014). Characteristics of the insect orders. Amazon. Characteristics of the insect orders with drawings and photographs to help you understand the differences between the different types of insect, and identify which order an insect is in, as well as fast facts about each insect order, and links to web pages with more detailed information. Many orders have separate sections about the life cycle of the insect as well as its habitat requirements, and fossil history.
"If all mankind were to disappear, the world would regenerate back to the rich state of equilibrium that existed 10, 000 years ago. If insects were to vanish, the environment would collapse into chaos." E. O. Wilson
There are over a million described species and many more waiting to be described and even more waiting to be discovered; some authorities say as many as 4 million insect species await discovery. In fact more than 50% of all described species (animal and plant) on earth are insects. In the UK there are around 24,000 species. In North America there are around 90,000 described species, but many more waiting official description (see the taxonomy page for more on this). They are in around 30 Orders, depending on which book you read. They range in size from less than 1 mm up to 20 cm in length.
Previously it was thought that the Myriapoda - Centipedes, Millipedes etc., were the closest living relative to the insects, but now some scientists believe that the Remipedia in the Crustacean Phylum are their closest living relatives. Both insects and Remipedia have similar brains, nervous systems and proteins.
The earliest fossil insects date back to 410 million years ago, but as these insects were already quite elaborate, the true origin may be much earlier, perhaps as early as 480 MYA in the Ordovician, around the same time as the earliest terrestrial plants. They were wingless and resembled modern springtails. Rhyniella precursor, a springtail found near Rhynie in N E Scotland dates from 410 MYA. The insects are thought to have started their colonisation of the land around 320 million years ago during the Carboniferous.
The secret of the success of the insects can be linked to the following features:
About 85% of the world's flowering plants rely on insects for pollination, that includes avout 35% of global crop production.