FOSSIL INVERTEBRATES/Insects 297 Figure Palaeodiversity of organisms Key to numbers: 1, bacteria and blue green algae; 2, fungi; 3, other algae; 4, single cell organisms; 5, sponges; 6, corals, etc.; 7, chitons, etc.; 8, snails; 9, nautiluses; 10, ceratites; 11, ammonites; 12, belemnites; 13, bivalves and tusk shells; 14, uncertain molluscs; 15, segmented worms; 16, trilobites; 17, spiders, etc.; 18, crustaceans (excluding seed shrimps); 19, seed shrimps; 20, millipedes, etc.; 21, insects; 22, lamp shells; 23, phoronids; 24, moss animals; 25, sea urchins, etc.; 26, primitive chordates; 27, graptolites; 28, problematica; 29, miscellaneous; 30, conodonts; 31, lampreys, etc.; 32, cyclostomes; 33, primitive fish; 34, sharks, etc.; 35, primitive bony fish; 36, advanced bony fish; 37, more bony fish; 38, amphibians; 39, reptiles; 40, birds; 41, mammals; 42, mosses, etc.; 43, ferns, etc.; 44, seed plants (excluding 45, flowering plants) Figure Relationship of insects with other arthropods Figure Major insect groups; apterygotes include springtails and silverfish Figure The two main groups of pterygotes are the paleopter ans and the neopterans, which are further divided into subgroups Paleopterans include dragonflies and mayflies Cockroaches and grasshoppers, along with stoneflies, stick insects, crickets, locusts, earwigs, termites, and praying mantises comprise the polyneopteran orders Paraneopteran orders include bugs and lice Holometabolous orders include beetles, lacewings, wasps, ants, bees, caddisflies, moths, butterflies, flies, and fleas