1. Creatures of the “Jointed Legs”
Phylum Arthropoda
Creatures of the “Jointed Legs”

2. Phylum Arthropoda I. Characteristics of Arthropods
A. Chitin exoskeleton divided into segments
(segmentation is known as metamerism –)
Individual segments are called tagmata.
B. Jointed Appendages
C. True Coelomates
D. Open circulatory system
E. Advanced nervous and muscular systems
F. Respiration by trachea, book lungs, body surface,
or gills
G. Sexes are usually separate males and females

3. II. We’ll look at six of the most common of the Arthropod classes
A. Class Insecta – The largest and most
successful class of organisms in the world.
B. Class Crustacea – mostly aquatic; shrimp, crabs,
lobsters, crayfish, etc.
C. Class Arachnida – spiders, mites and ticks
D. Class Chilopoda – venomous centipedes
E. Class Diplopoda - nonvenomous millipedes
F. Class Merostomata (Subclass Xiphosuridae) –
Only 1 living representative - The Horseshoe Crab

4. III. Classification – Subphylum Hexapoda A. Class Insecta
1. Three body segments – Head, Thorax and
Abdomen – Segments are called Tagmata
2. Three pairs of legs – all attached to the thorax
3. Some insects live socially, sharing a division of labor
4. Some insects carry out Metamorphosis
a. complete metamorphosis – significant change
such as that seen in butterflies or beetles
b. Incomplete metamorphosis – not so great a
change such as seen in crickets or grasshoppers
5. Defense includes stings, mimicry, protective or
warning coloration, secretions, bites, and sprays.

5. III. Classification A. Insecta (continued)
6. Excretion carried out by Malpighian Tubules.
7. Sense of hearing carried out by setae on tympanic structures, or by feeling substrate with their legs.
8. Visual reception is carried out with either simple eyes or compound eyes. Some can actually detect color.
9. Parthenogenesis (Strange asexual reproduction) in the life cycle of some Hymenopterans and Hemipterans.
10. Most have Sexual Reproduction with separate males and females.
11.Shedding or molting of the exoskeleton is called Ecdysis.

7. Complete Metamorphosis
Egg
Larva
Pupa
Adult

8. Incomplete Metamorphosis –
Egg
Nymph
Adult

9. Most Common Insect Orders: Now 30 orders recognized
Diptera – Flies and Mosquitos
Orthoptera – Grasshoppers, Crickets
Order Blattodea - Cockroaches
Coleoptera – Beetles
Lepidoptera – Butterflies and Moths
Hymenoptera – Ants, Bees, and Wasps
Isoptera – Termites
Hemiptera – True Bugs
Odonata – Dragonflies
Siphonaptera – Fleas
Neuroptera - Lacewings

11. Lady Beetle flying in slow motion
Wasp and Bee stings in slow mo

12. B. Arachnida 1. Two body segments –Cephalothorax & Abdomen
2. Four pairs or 8 legs
3. Eight simple eyes
4. Anterior appendages called chelicerae have fangs
5. Only two dangerous genera (genus) in the USA.
6. It is important to note that ALL spiders are venomous!
7. There are about 43,000 species of spider in the world!
Brown Recluse
(Hemolytic venom:
Attacks Living tissue)
Black Widow
(Neurotoxic venom:
Attacks nervous system)

13. Interesting spider venom tidbits:
The venom of the Black Widow is a neurotoxin,
and causes :
Paralysis

14. Interesting spider venom tidbits:
The venom of the Brown Recluse is a hemolytic toxin,
and causes
necrosis

15. Other Arachnids Dust Mite Scorpion Harvestman (Commonly misnamed
Daddy-Longlegs)
NOT venomous!

16. Other Arachnids:
1. Dust mites (about 40,000 species) live in house dust, and in mattresses; redbugs (chiggers) are mites.
2. Scorpions (about 1,400 species) feed largely on insects and spiders at night.
3. Harvestmen (about 5,ooo species) are harmless to to humans and protect themselves by excreting noxious secretions, and can escape by shedding legs.
4. Ticks have an anasthaetic and an anticoagulant in their saliva.

17. C. Crustacea (crabs, shrimp, lobsters, crayfish, pillbugs ) Pillbugs
1. Two pairs of antennae
2. Gills used for respiration
3. Usually five or more pairs of legs
including pincers called chelipeds.
4. Mostly aquatic – a few are
terrestrial. – Sowbugs; Pillbugs
5. Sharp tail structure is a telson
Pillbugs

18. More Crustaceans

19. Other Crustaceans
Blue Crayfish

20. “Centipedes – The creatures of a hundred legs”
D. Class Chilopoda
“Centipedes – The creatures of a hundred legs”
Numerous body segments with ONE pair of legs per segment – except the one behind the head and the last two. They DO NOT have 100 legs! (w/caveat)
2. Hollow fangs produce toxins to kill prey
3. Carnivorous – Eat only worms, insects, some small reptiles, or mammals. Some are slightly dangerous
through painful bites.
Scolopendra gigantea
A typical centipede

21. E. Class Diplopoda “ millipedes: creatures of a thousand legs”
1. Numerous body segments with TWO pairs of legs
per body segment, except the one behind the head
and the last two.
2. Notice the more rounded shape with (typically) shorter legs.
3. Produce a noxious secretion and coil up when threatened
4. Herbivorous – They eat decaying organic matter and leaf
litter.
A Typical Millipede

22. F. Class Merostomata also known as Xiphosurida Horseshoe Crab
1. Horseshoe shaped carapace or dorsal surface.
2. Long, fused telson, or tailpiece,
also found in crustaceans
3. Reproductive cycles very important
to shorebird migration.
Copper based blood used in
pharmacology.
Horseshoe Crab

23. Interesting tidbits: Insects are in the subphylum Hexapoda.
Centipedes and Millipedes are in a the subphylum Myriapoda .
Spiders, Mites, Ticks, Harvestmen, Scorpions, and Horseshoe
Crabs are in the Subphylum Chelicerata.
Lobsters, Crabs and Crayfish are in the subphylum Crustacea
The extinct Trilobites are in the Subphylum Trilobita.

24. All Homework due for ALL students by midnight of the next day!
TEST!!!
Next Class Period!!!
All Homework due for ALL students by midnight of the next day!