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Fig. 7.2

“primitive hexapods”. “basal orders” (= “Apterygota”). NEW ORDER! ca. 2000. ?. ?. ?. true INSECTS. A current hypothesis for the cladistic phylogeny of the insects and primitive hexapods. Fig. 7.2. Gullen & Cranston, 2005. The Basal or Apterygote ( wingless ) Orders. ARCHAEOGNATHA

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Fig. 7.2

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  1. “primitive hexapods” “basal orders” (= “Apterygota”) NEW ORDER! ca. 2000 ? ? ? true INSECTS A current hypothesis for the cladistic phylogeny of the insects and primitive hexapods Fig. 7.2 Gullen & Cranston, 2005

  2. The Basal or Apterygote (wingless) Orders ARCHAEOGNATHA (= MICROCORYPHIA)jumping bristletails THYSANURA (= ZYGENTOMA)silverfish, firebrats

  3. ARCHAEOGNATHA “Jumping bristletails” X-sec Shrimp-like profile; tail filaments relatively parallel, bristly. Primitive, spider-like, single-articulated jaws. Deocmposers. No economic significance.

  4. THYSANURA (ZYGENTOMA) “silverfish & firebrats” Flattened profile, don’t jump, tail filaments held close to 90 deg. apart. A few are economic pests, damaging cellulose & fabric. Thermobia, a firebrat. Giant neurons in tail filaments studied at UW.

  5. “Aquatic” Insects A polyphyletic, ecological assemblage of taxa. The aquatic lifestyle has arisen many times in insect evolution; only in a few orders is it the rule. In most, the immature stages are truly aquatic while the adult is a winged terrestrial form.

  6. other orders with aquatic species Holometabolous, Endopterygote TRICHOPTERA Hemimetabolous, Exopterygote PLECOPTERA Paleoptera ODONATA EPHEMEROPTERA AQUATIC INSECTS, an ecological (polyphyletic) group

  7. Importance of Aquatic Insects Most references to nymphs/larvae; some taxa beyond this lecture Natural World Nutrient cycle: decomposers Water quality: filter feeders Food Webs: prey & predators, e.g. salmon fry eat bugs Anthropophilic World Aquatic environmental quality indicators Medical/Disease vectors, especially mosquitoes, other flies Human Food (coryxid eggs; water bug wing muscle; fly pupae) Sport Fishing (Fly Tying)

  8. Life History & Physiological Aspects of Aquatic vs. Terrestrial Insects DevelopmentTerrestrial:variable rate Aquatic: Generally slower (colder temperature under water) RespirationTerrestrial:open system (siphon, physical gill, etc.) Aquatic:closed tracheal system (gills, cutaneous) with exceptions Water/Ion BalanceTerrestrial:conserve water fromdehydrationAquatic: conserve ions from dilution Nitrogen Waste RemovalTerrestrial:uric acid (conserveswater)Aquatic: ammonia (conserves energy)

  9. terrestrial (winged) adult aquatic immature Fish-eye view through the mind of the fisherman (superpredator). Fish as entomologists! EPHEMEROPTERA, mayflies

  10. wing pads gill covers gills 3 “tail filaments” = cerci Larva (nymph, naiad) Mayflies are predaceous or detritovores as nymphs. Adults do not feed. Adult

  11. Mayfly adult antennae are small; hindwing may be small or vestigal. forlegs hindwing

  12. larval molt, subimago molt, & adult

  13. ODONATA, dragon- & damselflies

  14. damselflies dragonflies

  15. labial mask All odonates are predators as both nymphs and adults.

  16. 2. grab 1. lunge dragonfly larva labial mask hydraulic feeding mechanism

  17. Some large dragonfly nymphs may take vertebrate prey!

  18. trachealtubes adult eclosion

  19. A tropical dragonfly. The wings are always held out at rest.

  20. Dragon flies have acute and fast vision. • Up to 10,000 eye facets (high resolution!) • Adaptations: small prey capture at high speed while flying & mate/mate competitor detection.

  21. Well-known “loop” configuration of mating odonates; male grasps female with tail claspers; transfers sperm from secondary sex organs on 2nd abdominal segment.

  22. A damselfly. Some are spider predators.

  23. Males of some dragonfly species are territorial, with traditional perches.

  24. Some ancient dragonfly relatives (“Griffinflies”) measured over two feet in wingspan. How could flying insects live at this scale?

  25. Orthopteroids i.e., cricket- or roach-like. • Nymphs fully aquatic, prefer highly oxygenated water. • Thoracic gills. • Two long cerci in nymphs & adults. PLECOPTERA, stoneflies

  26. thoracic gills Stoneflies are predators or detritovores as numphs; adults do not feed.

  27. wing pads Some insects can be active at near-freezing temperatures. A “winter” stonefly nymph, one species among various snow-active insects.

  28. Stonefly exuviae.

  29. TRICHOPTERA, caddisflies • Sister order to the Lepidoptera. • Moth-like. long, thread-like antennae hairy (vs. scaly) wings wings membranous (~transparent) reduced mouthparts Features distinguishing adult caddisflies from adult moths.

  30. scales A true moth.

  31. Caddisfly nymphs are predaceous or detritovores; adults do not feed. diverse larval cases (including none!)

  32. caddis fly larval cases TRICHOPTERA

  33. typical caddisfly larva without case from Gullen & Cranston 2000

  34. Life stages of an aquatic snout moth (Pyralidae).Parallel evolution of the caddisfly-like natural history.

  35. Halobates, an open water predaceous bug. Marine Insects Hydrophobic hairs on tarsi of Trochopus, a related genus. Egg phoresy: eggs laid on tail of seabird. all from Cheng 1976

  36. male skating male female Clunio californiensis, an open water marine midge (DIPTERA: Chironomidae) mating behavior all from Cheng 1976

  37. END

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