Arthropods Part 3

1. Arthropods Part 3

2. Subphylum MyriapodaClass Chilopoda: Centipedes • Active predators • Feed mostly on earthworms & insects • Prefer moist places • Bodies somewhat flattened dorsoventrally • Contain from a few to 177 segments • Each segment bears one pair of appendages • 1st appendages modified to form venom claws • Sexes are separate • All are oviparous • Producing eggs that hatch outside the body

6. Subphylum MyriapodaClass Diplopoda: Millipedes • “double-footed” • Cylindrical bodes contain 25-100 segment • Four thoracic segments bear one pair of legs each • Abdominal segments each have two pairs • Herbivores • Decayed plant & animal matter • Prefer dark moist places

7. Millipede

8. Millipede

9. Millipede

10. Giant African Millipede

11. Subphylum MyriapodaClass Insecta: Insects • Most numerous & diverse of all arthropods • ~1 million species named • Entomology • Study of insects • Differ from other arthropods by: • containing 3 pairs of legs • 2 pairs of wings • Range from less than 1 mm to 20 cm in length • Majority are less than 2.5 cm long

12. Subphylum MyriapodaClass Insecta: Insects • Distribution & Adaptability • Live in all habitats that can support life • Only a few are marine • Small size & well-protected eggs allow them to travel great distances by wind, water, & other animals • Cuticular exoskeleton • Gives insects much success

13. Subphylum MyriapodaClass Insecta: Insects • External Features • Tagmata are head, thorax & abdomen • Cuticle composed of 4 plates (sclerites) • Tergum – dorsal notum • Ventral sternum • Pair of lateral pleura • Legs are often modified for special purposes • Terrestrial forms walking legs with terminal pads and claws as in beetles • Can be sticky for walking upside down (house fly) • Hind legs adapted for jumping (grasshopper and crickets) • First pair of legs modified for burrowing (mole cricket) • Paddle-shaped for swimming (water bugs, many beetles) • Forelegs modified for grasping pray (praying mantis)

14. House Fly

15. Grasshopper

16. Mole Cricket

17. Mole Cricket

18. Praying Mantis eating Grasshopper

19. Subphylum MyriapodaClass Insecta: Insects • Wings & the Flight Mechanism • Wings may be: • Thin and membranous (flies) • Thick and stiff (beetles) • Parchment-like (grasshoppers) • Covered with scales (butterflies, moths) • With hairs (caddisflies) • Wing movement controlled by thoracic muscles • Direct flight muscles • Attached to a part of the wing itself • Indirect flight muscles • Not attached tot the wing • Cause wing movement by altering the shape of the thorax

20. Direct Flight Muscles Indirect Flight Muscles

21. Subphylum MyriapodaClass Insecta: Insects • Wings and Flight Mechanism • Flight speeds vary • Fastest flyers usually have narrow, fast-moving wings with a strong tilt • Sphinx moths and horse flies are said to achieve about 48 km/hr (30 miles/hr) • Dragonflies 40 km/hr (25 miles/hr)

22. Subphylum MyriapodaClass Insecta: Insects • Reproduction – • Sexes are separate • Fertilization is internal • They have various means of attracting mates: • Emit a chemical (pheromone) that can be detected for a great distance (moths) • Flashes of lights (fireflies) • Sounds and color signals, etc • Sperm are stored in the seminal receptacle of a female • numbers sufficient to fertilize more than one batch of eggs • Many insects mate only once during their lifetime

23. Subphylum MyriapodaClass Insecta: Insects • Behavior & Communication • Responsive to stimuli are both internal (physiological) or external (environmental) • Much of the behavior is “innate” • entire sequences of actions apparently have been programmed • Insects communicate with other members of their species by chemical, visual, auditory, and tactile signals • Chemical signals take the form of “pheromones” • Sound production and reception is not present in all insects • Tactile communication includes tapping, stroking, grasping, and antennae touching

24. Subphylum MyriapodaClass Insecta: Insects • Social Behavior • Rank high in the animal kingdom in the organization of social groups • Some groups are temporary and uncoordinated • feeding gatherings of aphids • Some are coordinated for only a brief time • tent caterpillars that join in building a home web and a feeding net • Some have a complex social life • honeybees, ants, and termites

25. Subphylum MyriapodaClass Insecta: Insects • Honeybees have one of the most complex social organizations in the insect world • Organization continues for a more or less indefinite period • As many as 60,000 to 70,000 may live in a single hive • There are three casts • Queen – a single sexually mature female • Drones – a few hundred sexually active males • Workers – thousands of sexually inactive genetic females • Take care of young, secrete wax to build the six-sided cells on the honeycomb, gather nectar from flowers, manufacture honey, collect pollen, and ventilate and guard the hive

26. Subphylum MyriapodaClass Insecta: Insects Honeybees – • Casts are determined partly by fertilization and partly by what is fed to the larvae • Drones develop parthenogenetically from unfertilized eggs • Queens and workers develop from fertilized eggs • “Royal jelly” is fed to larvae that will become queens • “Worker jelly” is fed to ordinary larvae • Pheromones from the queen prevent female workers from maturing sexually

27. Beehive

28. Queen Bee

29. Drone Bee

30. Worker Bee

31. Worker bee with pollen