1. The Hexapods and Myriapods: Terrestrial Triumphs
Chapter 15
Zoology

2. The Insects
750,000 + species insects described, but may be 30 million species undescribed.
Many adaptations make insects one of the most successful terrestrial animals.
Exoskeleton for water conservation
Tracheal System for gas exchange
Metamorphosis
Many types of mouth parts
Flight

3. Subphylum Myriapoda
Myriad, ten thousand + podus, foot; millipedes and centipedes.
Two tagmata (head and trunk)
All are terrestrial

4. Class Diplopoda – The Millipedes
Have 11 – 100 trunk segments, each with two pairs of appendages.
Each segment is actually the fusion of two segments; internally there are two ganglia, two pairs of ostia, etc. in each segment.
Most are round.
Feed on decaying plant matter.
Roll into a ball for defense.
Some excrete hydrogen cyanide as a deterrent to predators.

5. Giant African Millipede
See it move!

6. Class Chilopoda – The Centipedes
15+ trunk segments, each with a pair of legs.
Flattened body
Last pair of legs is modified into long sensory appendages.
Nocturnal predators
Poison claws (maxillipeds) on first segment capture other invertebrates and small vertebrates.
Males lay down a silk web and places a spermatophore for female.

7. Predatory Centipede vs. Mouse

8. Subphylum Hexapoda Class Insecta
three tagmata (head, thorax, and abdomen)
Five pair of head appendages
Three pairs of legs on thorax

9. Fig. 20.8

10. Fig. 20.4a

11. Specialized Mouthparts
Modified mouthparts have allowed insects to diversify and take advantage of many different food sources.
Modify generic structures for various food sources.
Generalized Insect Mouthparts

12. Fig a
Chewing Mouthparts

13. Fig b
Piercing Mouthparts

14. Fig d
Siphoning Mouthparts

15. Fig e
Sponging Mouthparts

16. Antennae Modifications
Fig. 20.5

17. Insect Flight
Direct or Synchronous Flight – muscles attach at the base of wings contract for downward thrust and muscles attach to the exoskeleton contract for upward thrust. Requires two nerve impulses for upward and downward strokes. Ex. Butterflies, dragonflies, grasshoppers.
Indirect or Asynchronous Flight – muscles act to change the shape of the exoskeleton for both strokes. Only one nerve impulse for 50 cycles. Ex. Flies and wasps.

18. Indirect Insect Flight
Indirect flight muscles allow wings to beat faster than neural transmission.
Dorsoventral and longitudinal muscles.
Flexible thorax.

19. Review of Insect Physiology
Digestion – three part tract.
Respiration – most use a tracheal system
Circulation – open circulatory system
Nervous – ventral nerve cord with some segmental ganglion.
Excretion – Malpighian tubules with uric acid.

20. Fig

21. Fig. 20.Fig. 20a

22. Fig. 20.Fig. 20b

23. Tracheal Systems in Insects
The tracheal system of insects
Consists of tiny branching tubes that penetrate the body
Tracheae
Air sacs
Spiracle
(a) The respiratory system of an insect consists of branched internal tubes that deliver air directly to body cells. Rings of chitin reinforce the largest tubes, called tracheae, keeping them from collapsing. Enlarged portions of tracheae form air sacs near organs that require a large supply of oxygen. Air enters the tracheae through openings called spiracles on the insect’s body surface and passes into smaller tubes called tracheoles. The tracheoles are closed and contain fluid (blue-gray). When the animal is active and is using more O2, most of the fluid is withdrawn into the body. This increases the surface area of air in contact with cells.

24. The tracheal tubes Supply O2 directly to body cells. Body cell Air sac
Tracheole
Tracheoles
Mitochondria
Myofibrils
Body wall
(b) This micrograph shows cross sections of tracheoles in a tiny piece of insect flight muscle (TEM). Each of the numerous mitochondria in the muscle cells lies within about 5 µm of a tracheole.
2.5 µm
Air

25. Tracheal System Limits Size
See the Giant Weta

26. Copyright © The McGraw-Hill Companies, Inc
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Insect Excretion

27. 3 Kinds of Insect Metamorphosis
Ametabolous Metamorphosis – only difference between larvae and adult are size; both are wingless. Silverfish, Order Thysanura.
After Flight…
Hemimetabolous Metamorphosis – develop from egg to adult has several stages (instars) with smaller versions of adults called nymphs. Immature nymphs have no wings or genitalia until adult.

28. 3 Kinds of Insect Metamorphosis
Holometabolous Metamorphosis – after hatching from egg, immatures are called larvae (very different body form than adult). After several instars, the last larval molt forms a pupa – undergoes radical body form change.
Protective case may enclose pupal stage:
Moths use silk to make a cocoon.
Butterflies use the larval exoskeleton to make a chrysalis.
Adult emerges from case very different in body form – eclosion.

29. Incomplete or Hemimetabolous Metamorphosis
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Incomplete or Hemimetabolous Metamorphosis
From Hickman/Roberts/Larson, Integrated Principles of Zoology, 11th ed., Copyright © 2001 The McGraw-Hill Companies.

30. Complete or Holometabolous Metamorphosis
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Complete or Holometabolous Metamorphosis
From Raven/Johnson, Biology, 3rd ed., Copyright © 1999 The McGraw-Hill Companies.

31. You Decide?
Fig

32. Hemimetabolous - insects hatch looking much like adults
Hemimetabolous - insects hatch looking much like adults. Nymphs gradually attain adult form and wings.
Holometabolous - young very different from adults. Pupal stage metamorhosis into adult.

33. Insect Orders

34. Order Collembela Antennae with 4-6 segements No compound eyes
Six segments in abdomen
Furcula for jumping
No wings
Springtails

35. Order Thysanura Tapering abdomen Long antennae, scaled on body
No wings
Silverfish

36. Order Odonota Elongate, membraneous wings. Long, slender abdomen
Large compound eyes
Dragonflies,damselflies

37. Order Mantodea Long prothorax Legs armed with spine for grasping prey
Mantids
Missouri Native –Chinese mantis, Tenodera aridifolia

38. Blattaria Oval, flattened body
Head concealed by an extension of prothorax
Cockroaches

39. Order Orthoptera Long, narrow forewing Hindwing is broader
Chewing mouthparts
Grasshopper

40. Order Dermaptera Elongate, chewing pouthparts
Abdomen with unsegmented forcepslike cerci
Short wings
Earwigs

41. Order Isoptera Workers are white and wingless
Abdomen broadly joins thorax
Reproductive forms with wings
Termites

42. Order Hemiptera Cicadas, leafhoppers, aphids
Piercing-sucking mouthparts
Wings membraneous
Basal portion is leathery
Apical portion of wing is membranous
Cicadas, leafhoppers, aphids

43. Order Coleoptera
Hard front wings meet midline to form a cover (elytra)
Hindwings membranous
Chewing mouthparts
Beetles, largest insect order; 350,000+ species

44. Order Lepidoptera Wings are broad and covered in scales
Mouthparts form a sucking tube
Butterflies and moths

45. Order Diptera
One pair of well-developed wings, other pair reduced to knoblike halteres
Mouthparts variously modified, but never chewing.
Flies

46. Order Hymenoptera Four membranous wings
Well-developed ovipositor,sometimes modified into a sting
Mouthparts for biting and lapping.
Social and solitary forms
Bees, wasps, ants

47. Order Phthiraptera Small, wingless, ectoparasites
Dorsoventrally flattened
Sucking/chewing mouth parts
Lice

48. Order Siphonaptera Flattened laterally
Sucking mouthparts, ectoparasites
Jumping legs
Fleas

49. The End
What order am I?