Handout -- Insect orders and the timeline of insect evolution

Transcription

1 Handout -- Insect orders and the timeline of insect evolution The Class Hexapoda consists of 31 insect Orders (See list below). I will expect you to know the 31 insect orders and a little about each one (for example, are most species herbivores, predators, or parasites). Please also try to learn the order of the geological time periods. You do not have to remember the exact dates for each in millions of years, but you will have to remember that the Jurassic came after the Silurian. The easiest way for you to learn these names is for you to come up with a simple pneumonic device. We will, therefore have a contest: In your spare time, try to come up with a simple phrase such that each word begins with the letter of each period. The order of first letters will have to be COSDCPTJC. I will award a prize for any really catchy phrases (or, even better, poems). Good luck! Assuming that no one comes up with a really catchy phrase you will simply have to learn them by memorizing the order, Cambrian, Ordovician, Silurian, Devonian, Carboniferous Major events in insect evolution: I. Origin of wingless hexapods -- the earliest hexapods probably arose in the Silurian. We have well-preserved fossils from the Early Devonian. The Silurian was the period when the first land plants appeared in the fossil record, and insects probably colonized land shortly afterwards. II. Evolution of wings -- winged insects first appeared in the fossil record in the Carboniferous period (350 mya). They almost certainly arose much earlier than that (probably the Devonian) because the earliest fossils of winged insects had well-developed and complex wings. III. Evolution of wing folding -- Wing folding evolved in the Carboniferous period, not too long after the evolution of wings in the first place. Wing folding characterizes all Neopterous insect orders (all orders except Odonata and Ephemeroptera), and has allowed insects to inhabit burrows, nests, tunnels, and generally protect themselves and their wings. IV. Evolution of metamorphosis -- Metamorphosis evolved sometime late in the Carboniferous or early Permian. What followed was another radiation in insect diversity. V. End Permian Extinction -- At the end of the Permian (230 to 245 mya) there was a major extinction event that eliminated many orders of very primitive winged insects. I refer to these orders in the lecture as the Paleozoic insect orders. This may have cleared the way for a major radiation in the remaining insect orders and especially the Holometabola. VI. Angiosperm (flowering plant) radiation -- Insect diversity increased dramatically following the origin of the flowering plants (in the Cretaceous). Insects adapted rapidly to the new resource and evolved new methods of feeding and intimate associations with angiosperm life histories

2 Insects are very diverse From: Gullan & Cranston, The Insects, Third Ed., 2005

3 Annelida (worms) Onychophora (velvet worms) Tardigrada (water bears) Myriapoda (millipedes, etc.) Trilobita (extinct) Chelicerata (spiders, etc.) Arthropoda Crustacea (crabs, etc.) Phylogeny of the Arthropoda Hexapoda (insects)

4 Phylogeny of the insect orders From: Gullan & Cranston, The Insects, Third Ed., 2005

5 Fossil record of the insect orders From: Gullan & Cranston, The Insects, Third Ed., 2005

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7 A complete list of the 31 living insect orders Apterygota (wingless insects) 1. Protura (Prot, first; ura, tail) = proturans; ~500 species. 2. Collembola (Coll, glue; embola, a wedge) = springtails; ~4000 species. 3. Diplura (Dipl, two; ura, tail) = two-pronged bristletails; ~500 species. 4. Archaeognatha (Archeo, old; gnath, jaw) = jumping bristletails; ~25 species. 5. Zygentoma = Thysanura (Thysan, fridge; ura, tail) = silverfish; ~400 species. Pterygota (winged insects) I. Hemimetabola (gradual development) Paleopterous orders (=primitive winged) orders 6. Odonata (Odon, a tooth) = dragonflies and damselflies; ~5500 species. 7. Ephemeroptera (Ephemero, brief; ptera, wing) = mayflies; ~2500 species. "Orthopteroid" orders (=Polyneoptera) 8. Plecoptera (Pleco, pleat; ptera, wing) = stoneflies; ~1200 species. 9. Embioptera (Embio, lively; ptera, wing) = webspinners, embiids; ~2000 species. 10. Phasmida (Phasm, phantom) = stick insects; ~2000 species. 11. Orthoptera (Ortho, straight; ptera, wing) = grasshoppers, locusts, crickets, katydids; ~20,000 species. 12. Dermaptera (Derma, skin; ptera, wing) = earwigs; ~1000 species. 13. Grylloblattodea (Gryll, cricket; blatta, cockroach) = rock crawlers, ice bugs; ~25 species. 14. Mantophasmatodea [newest insect order] (Mantid, soothsayer; Phasm, phantom) = heel walkers; ~20 species. 15. Isoptera (Iso, equal; ptera, wing) = termites; ~2000 species. [may actually belong within the Blattodea] 16. Blattodea (Blatta, cockroach) = cockroaches; ~4200 species. 17. Mantodea (Mantid, soothsayer) = mantids; ~2000 species. 18. Zoraptera (Zor, pure; ptera, wing) = zorapterans; ~25 species. "Hemipteroid" (sucking) orders (=Paraneoptera) 19. Psocoptera (Psoco, rub small; ptera, wing) = booklice, barklice; ~2000 species. 20. Phthiraptera (phthir, lice; a, without; ptera, wing) = lice; ~3000 species. 21. Thysanoptera (Thysano, a fringe; ptera, wing) = thrips; ~400 species. 22. Hemiptera (Hemi, one-half; ptera, wing) = true bugs; ~82,000 species. Sometimes this order is treated as two orders: Heteroptera & Homoptera.

8 II. Holometabola (complete development) "Primitive" Holometabola 23. Coleoptera (Coleo, sheath; ptera, wing) = beetles; ~375,000 species. 24. Neuroptera (Neuro, nerve; ptera, wing) = lacewings and relatives; ~5000 species. Sometimes treated as three orders (as in your phylogeny of the insect orders) Neuroptera = lacewings, antlions, owlflies Megaloptera = dobsonflies, alderflies Raphidioptera = snakeflies 25. Hymenoptera (Hymen, membrane; ptera, wing) = sawflies, wasps, bees, and ants; ~130,000 species. Orders related to Lepidoptera 26. Trichoptera (Tricho, hair; ptera, wing) = caddisflies; ~7,000 species. 27. Lepidoptera (Lepido, scale; ptera, wing) = butterflies and moths; ~175,000 species. Orders related to Flies: 28. Mecoptera (Meco, long; ptera, wing) = scorpionflies; ~500 species. 29. Siphonaptera (Siphon, a tube; aptera, wingless) = fleas; ~2000 species. 30. Strepsiptera (Strepsi, twisted; ptera, wing) = twisted-winged parasites; ~400 species. 31. Diptera (Di, two; ptera, wing) = true flies; ~125,000 species.