1. Subphylum Chelicerata
Phylum Arthropoda

2. Characteristics Their bodies are composed of two tagmata:
Cephalothorax
Abdomen
Six pairs of cephalothoracic appendages that include:
Mouthparts
Pedipalps – sensory organs near mouth parts
4 pairs of walking legs
No antennae
Suck liquid food from their prey

3. Chelicerata Evolution

4. Classes
Class Merostomata
Class Phycnogonida
Class Arachnida

5. Class Merostomata Ancient group sometimes called “living fossils”
2 subclasses:
Subclass Eurypterida
Subclass Xiphosurida

6. Subclass Euryterida Eurypterids, or water scorpions Extinct
Largest fossil arthropods
Abdomen has 12 segments and a spike like telson (last segment, or “tail”)

7. Subclass Xiphosurida Horseshoe crabs Ancient marine group
Have an unsegmented horseshoe shape carapace (hard dorsal shield) and a broad abdomen
Feeds on worms and small molluscs

8. Class Pycnogonida Sea spiders 1000 species known
Range in length from 2mm m
Contain 5 or 6 pairs of legs
Males bear a subsidiary pair of legs (ovigers) in which they carry developed eggs (absent in females)
Small head with a raised projection with a pair of simple eyes

9. Class Arachnida Spiders, scorpians, ticks, mites, daddy longlegs etc.
Free-living
Common in warm, dry regions
80,000 species – first arthropods to move into terrestrial habitats
Two tagmata:
Cephalothorax – head and thorax
Abdomen – may or may not be segmented, contain reproductive organs and respiratory organs
predators- have fangs, claws, venom glands or stingers

10. Dust Mite
Tick
Scorpion
Spider

11. Class Arachnida
Most arachnids are harmless to humans and actually do much good by destroying injurious insects.
Feed by releasing digestive enzymes over or into their prey and then sucking the predigested liquid
Few, such as black widows and brown recluse spiders, can give dangerous bites
Scorpians can give painful stings
Ticks and mites can be carriers of disease and cause annoyances or irritations.
Mites can also damage a number of important food

12. Orders
Order Araneae
Order Scorpiones
Order Opillones
Order Acari

13. Order Araneae Spiders 40,000 species
Liquefies preys tissues with digestive fluid and sucks the resulting broth into its stomach
Use teeth to crush or chew prey
Have 8 simple eyes- used specifically for detecting movement (some, such as the jumping spider, can see images)
Contain 2 or 3 pairs of spinnerets (used to make webs)

14. Order Araneae Reproduction: Courtship rituals
Male spins a small web and deposits sperm on it and they picks up the sperm to be stored in special cavities of his pedipalps
When he mates, he inserts his pedipalps into the female genital opening to store the sperm in his mates seminal receptacles
Female lays her eggs in a silken net, which she may carry or attach to a web or plant
A cocoon may contain hundreds of eggs
Eggs will hatch in approximately 2 weeks
Young usually remain in the sac for a few weeks and molt once before leaving
Total molts range from 4-12 before reaching adulthood

15. Order Araneae
Spiders are very timid creatures and are typically allies in the continuing battle with insects and other arthropod pests
Venom used to kill prey is typically harmless to humans
Poisonous spiders only bite when threatened
Even tarantulas are NOT dangerous, they rarely bite and if they do are as serious as a bee sting
However, the black widow and brown recluse can give serious to fatal bites

16. Order Scorpiones Scorpions Most ancient of terrestrial arthropods
1,400 species worldwide
Common in tropical regions
Generally secretive, hiding in burrows and under objects by day and feeding at night
Feed on insects and spiders

17. Order Opiliones Harvestmen or “Daddy longlegs” 5,000 species
Abdomen and cephalothorax are rounded
Have only 2 eyes
Not venomous and harmless to humans
Unique because they are the only arachnids with a penis for direct transfer of sperm

18. Order Acari Ticks and mites
Most medically and economically important group of arachnids
40,000 species have been described but scientists estimate 500,000 to 1 million species exist
Mites are typically 1mm or less but some ticks can be 2mm-3cm
Most are free-living