Kingdom – Animalia
Phylum – Arthropoda
Subphylum- Chelicerata
Class – Arachnida
From microscopic mites to the nearly half pound Goliath birdeaters of South America, arachnids come in a range of sizes. Globally, there are approximately 100,000 known species of arachnids in 11 orders.
Arachnids have:
- two tagmata (distinct body regions):
- prosoma or cephalothorax (head and chest combined)
- opisthosoma (abdomen).
- no antennae.
- no wings.
Order Araneae: Spiders
Spiders have:
- a cephalothorax and an abdomen.
- spinnerets to produce silk.
- pedipalps (“mini-legs”) in front of mouth, used to grab prey.
- fangs to bite prey.
- most have venom glands.
- 650 species in Illinois.
Order Acari: Mites & Ticks
The Acari have:
- two tightly connected tagmata appearing as one unit.
- lost the eyes of many species.
- modified chelicerae for piercing, sucking, or biting.
- 20 species of ticks and ~10,000 species of mites in Illinois.
Order Pseudoscorpionida: Pseudoscorpions
- are small (2-8 mm)
- have chelate (pincer-like) pedipalps
- lack the long tail of a scoprion
- are found in all terrestrial habitats
- have 28 species in Illinois
Order Scorpiones: scorpions
Scorpions have:
- eight legs
- chelate (pincer-like) pedipalps
- narrow tail with venomous stinger
- one Illinois species
Order Opiliones: Harvestmen or Daddy long-legs
Harvestmen have:
-
- small round bodies.
- the two tagmata are tightly connected, appearing as one unit.
- long thin legs.
- pedipalps to hold food.
- no venom glands.
- 19 species in Illinois.
- one pair of eyes.
- Araneae – spiders – 50,000
- Acari – mites and ticks – 40,000
- Scorpiones – scorpions – 1,100
- Amblypygi – tailless whip scorpions – 100
- Pseudoscorpiones – psuedoscorpions – 2,000
- Solifugae – solpugids – 900
- Opiliones – harvestmen – 6,500
- Palpigradi – micro whipscorpions – 60
- Ricinulei – hooded tickspiders – 58
- Schizomida – shorttailed whipscorpion – 230
- Thelyphonida/Uropygi – whip scorpions