1. Arthropods Part 3

2. Subphylum Myriapoda Class 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 Myriapoda Class Diplopoda: Millipedes
“double-footed”
Cylindrical bodes contain 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 Myriapoda Class 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 Myriapoda Class 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 Myriapoda Class 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 Myriapoda Class 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 Myriapoda Class 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 Myriapoda Class 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 Myriapoda Class 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 Myriapoda Class 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 Myriapoda Class 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 Myriapoda Class 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