Terrestrial Mandibulates

1. Terrestrial Mandibulates Chapter 20

2. I. Characteristics of Subphylum Uniramia • Body tagmata: head, thorax, abdomen • 1 pair of antenna; appendages uniramous • Primarily terrestrial

3. II. Class Chilopoda A. Characteristics • Found under logs, bark, and stones • Carnivorous, eating earthworms, cockroaches, and other insects • House centipede has 15 pairs of long legs • Most are harmless but some tropical ones are dangerous

4. B. Body Structure • Flattened bodies with up to 177 somites • 1st body segment has poisonous claws • Head: 1 pair antennae, 1 pair mandibles, 1-2 pairs maxillae • Eyes on sides of head are groups of ocelli • Separate sexes • Some lay eggs; some viviparous • Young resemble small adults

5. III. Class Diplopoda A. Characteristics • Less active than centipedes • Eat decayed plants; a few eat living plants • Slow moving; roll into a coil for defense • Some secrete toxic or repellant substances from special glands on side of body

6. B. Body Structure • 2 pairs of legs per somite • Bodies have 25-100 somites • Head: 2 clusters of simples eyes, 1 pair of antennae, mandibles, and maxillae • Female lays eggs in nest and guards them • Larvae have only 1 pair of legs per somite

7. IV. Class Insecta A. Diversity • Most diverse and abundant of all arthropods • Estimated at 1 million species • Found in nearly all habitats except sea • Most animals and plants have insect parasites externally and internally • Range in size from 1 mm to 20 cm; tropical insects tend to be larger

8. B. Adaptability • Flight and small size makes insects widely distributed • Well-protected eggs can withstand rigorous conditions and are easily dispersed • Structural and behavioral adaptations give them access to many possible niches • Some insects are adapted to coexist with one plant species • Exoskeletons allows for desert survival

9. C. External Form & Function 1. Head • 1 pair of large compound eyes • 1 pair of antennae; vary greatly in form; feel, taste, and hear • Mouthparts: labrum, pair of mandibles and maxillae, a labium, an a hypopharynx

10. Insect Heads

11. 2. Thorax • Prothorax, mesothorax, metathorax; each has a pair of legs • Mesothorax and metathorax each have wings • Wings have double membrane with veins (strengthens and identifies insects) • Legs end in terminal pads and claws • Some legs are modified for special purposes: hindlegs of grasshopper for jumping; forelegs of preying mantis for grasping prey; honeybee legs for collecting pollen

12. Insect Legs

13. 3. Abdomen • 9-11 segments ending in a pair of cerci • Larval or nymph forms may have appendages not in adults • External genitalia at end of abdomen

14. D. Flight 1. Wings • Outgrowth of cuticle from meso- and metathoracic segments • Diptera (flies) have only one pair; rest have 2; flies have halteres (knobby reduced wings) that provide balance • Lice, fleas, and nonreproductive ants and termites are wingless • Wings for flight are thin and membranous; thick horny front ones of beetle are protective; butterflies have scales on wings

15. Insect Wings

16. 2. Muscles • Direct flight muscles attach to wing • Indirect flight muscle changes shape of thorax which then moves wings • Dragonflies and cockroaches use direct muscles to fly • Bees, wasps, and flies move indirect muscles • Beetles and grasshoppers use combination • Wings move in figure-8 • Wing beats vary from 4/second (butterflies) to over 1000/second (midges)

17. E. Internal Form and Function1. Digestive System • Mouth seizes and crushes food; salivary glands to aid in digestion; some insects have sucking mouthparts; flies have lobes that absorb food • Gizzard grinds food; midgut digests and absorbs food; hindgut absorbs water • Most insects feed on plant tissue or juices • Some ants and termites cultivate fungus gardens • Some insects are predators or are parasites (hyperparasites parasitize parasitic insects)

18. 2. Circulatory System • Tubular heart moves hemolymph through dorsal aorta • Heartbeat peristalic wave • Accessory organs move hemolymph into wings and legs • Hemolymph has plasma and amebocytes but does not use oxygen transport

19. 3. Respiratory System • Tracheal system a network of thin tubes branched throughout insects body • Spiracles open to trachea; 2 on thorax and 7-8 on abdomen • Valve on spiracle prevents water loss and acts as dust filter • Tracheae branch into fluid filled tracheoles that reach individual body cells allowing gas exchange

20. 4. Excretion • Malpighian tubules excrete uric acid • Rectal glands reabsorb chloride, sodium, and water allowing other wastes to be excreted

21. 5. Nervous System • Fused ganglia • Neurosecretory cells in brain control molting and metamorphosis

22. 6. Sense Organs a. Mechanoreception • Touch, pressure, and vibration are picked up by sensilla ( single hair-like seta or organ) • Sensilla on antennae, legs, and body

23. b. Auditory Reception • Sensilla or tympanal organs may detect airbourne sounds • Organs found on Orthoptera, Homoptera, and Lepidoptera • Organs in legs can detect vibrations on ground

24. C. Visual Reception • Ocelli monitor light intensity but do not form images • Compound eyes have ommatidia like crustaceans • See simultaneously in almost all directions; image is myopic and fuzzy • Flying insects can process 200-300 image flashes per second • Bees use UV light but can not see red

25. D. Chemoreception & Other Senses • Sensory cells located in sensory pits located on mouthparts, antennae, and legs • Can detect some odors kilometers away • Feeding, mating, habitat selection, host selection all done though use of chemoreceptors • Cells on legs and antennae detect temperature changes, humidity, and gravity

26. 7. Muscular System • Muscles are cross-striated • Strength of muscle is related to cross-sectional area

27. F. Reproduction • Sexes are separate • Some insects use phermones, light, sound, color signals, courtship behaviors as attractant • Sperm deposited in vagina during fertilization • May lay a few eggs and care for young or lay many eggs • Eggs laid on host plant or animal

28. G. Metamorphosis and Growth • Most insects change form after hatching from egg • Each stage between molts is called an instar • Wings develop during last stage when useful during reproduction

29. 1. Homometabolous • 88% of insects • Egg, larval growth (may have several instars), pupal differentiation, adult reproduction • Pupa usually formed over winter, adult emerging in spring

30. 2. Hemimetabolous • Gradual metamorphosis • Grasshoppers, cicadas, mantids, true bugs, mayflies, dragonflies • Young are called nymphs • Egg, nymph, adult

31. 3. Direct Development • Young similar to adults just smaller in size • Silverfish and springtails, primarily wingless insects • Egg, juvenile, adult

32. 4. Physiology of Metamorphosis • Regulated by hormones produced by brain and ganglia • Molting hormone produced in response • Molting continues as long as juvenile hormone produced • With each instar, less and less juvenile hormone produced, until 0 is produced and adult emerges • Adults do not molt

33. H. Diapause • Period of dormancy in life cycle independent of conditions; genetically determined but may be triggered by environmental cues • Usually active growth triggers diapause • Winter dormancy—hibernation • Summer dormancy—estivation • Any life stage may become dormant to survive adverse conditions

34. I. Defense • Protective coloration, warning coloration, mimicry are protective adaptations • Also repulsive odors and tastes (stink bugs) or may spray irritating chemicals (bombardier beetle) • Some are aggressive (bees and ants)

35. J. Behavior and Communication • Well developed senses lead insects to respond to many stimuli • Most behavior is innate but some is learned

36. 1. Phermones • Chemicals secreted by one individual to affect behavior of another individual • Attract opposite sex, trigger swarming, fend off aggression, and mark trails • Bees, wasps, ants recognize nestmates and trigger alarms in response to invaders • Phermones used to attract and trap insects

37. 2. Sound Production & Reception • Sounds used as warnings, announcing territory, and courtship songs • Sounds may be made by chirps or rubbing of body parts

38. 3. Tactile Communication • Tapping, rubbing, grasping, and antennae touching • Bioluminescence

39. 4. Social Behavior • True societies as demonstrated by bees, termites, and ants have developed a complex social life as a means to perpetuate their species. • The societies exhibit a caste system which involves all stages in the life cycle, involve complex communication, and division of labor. • Honey bees have 3 castes: queen (single sexually mature female), drones (few hundred sexually mature males), and workers (thousands of sexually inactive females). • Termites and ants have several fertile males (kings) and females (queens); sterile individuals are workers and soldiers. Soldiers have larger heads and mandibles for defense.

40. Paper Wasps

41. Honey Bee Waggle Dance

42. Queen ant and male

43. Insects and Humans1 & 2 Beneficial/Harmful Insects • Insects produce products that humans utilize like honey, beeswax, silk, shellac • Insects also pollinate $10 billion dollars worth of human food crops in the US. • Some insects prey on other insects humans consider pests. • Some insects are agricultural/horticultural pests • Other insects transmit diseases, parasitize humans, or destroy property.

44. 3. Control of Insects • Insect play an important role in the food web since they are food sources for many organisms and their removal would have a cataclysmic effect. • Control of insects through insecticides has a lasting effect on the environment since many insecticides accumulate in the body tissues of larger organisms, eventually harming them as well. • Biological controls utilize other predatory insects, toxic strains of bacteria or viruses, engineering plants with toxins, releasing sterile males, or altering reproduction rates through the use of hormones.

45. Orthoptera (grasshoppers, crickets, katydids, and cockroaches) Isoptera (termites) Dermaptera (earwigs) Anoplura (sucking lice) Hemiptera ("true" bugs) Homoptera (aphids, mealy bugs, and cicadas) Ephemeroptera (mayflies) Odonata (dragonflies and damselflies) Neuroptera (dobsonflies and lacewings) Coleoptera (weevils, ladybugs, and beetles) Lepidoptera (butterflies and moths) Diptera (mosquitoes, flies, and gnats) Siphonaptera (fleas) Hymenoptera (bees, wasps, and ants)