Subclass Acari
- Ticks and mites
- Most very tiny (< 1 mm), except for ticks
- Some are external parasites
- Very diverse; typically divided into two or more orders or superorders
- • Parasitiformes are the ticks and various mostly parasitic mites
- • Acariformes are a large, diverse group of mites (including parasitic forms)
- May be polyphyletic
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Hard Tick, Dermacentor sp. (O. Parasitiformes); CA; a blood-feeding parasite
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American Dog Tick, Dermacentor variabilis (O. Parasitiformes); NE
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Blue Oat Mite, Penthaleus sp. (O. Acariformes); AZ; feeds on plants
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Whirligig Mite, Anystis sp. (O. Acariformes); AZ; aquatic
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A predatory Snout Mite (Family Bdellidae, O. Acariformes), AZ
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Prostigmatid (left) & Oribatid (right) Mites (O. Acariformes); AZ; from leaf litter
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Order Araneae
- Spiders
- 36,000 Species
- Most are predators
- Chelicerae modified into venom fangs
- Silk glands and spinnerets
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Western Black Widow, Lactrodectus hesperus, female in ventral view
See also labeled photo.
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Wolf Spider, Hogna sp. (Lycosidae); KY
See also labeled photo.
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Chilean Rose Tarantula, Grammastola rosea; tarantulas are large, primitive spiders
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Nursery Web Spider, Thaumasia
sp.; Ecuador
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Banded Garden Spider, Argiope trifasciata; Kenya
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Goldenrod Crab Spider, Misumena vatia; ME
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Long-jawed Orb Weaver. Tetragnatha sp. (Tetragnathidae); AZ
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Jumping Spider Phidippus sp. (Salticidae); AZ
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Marbled Cellar Spider Holocnemus pluchei (Pholcidae); AZ (introduced from Mediterranean region)
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Order Opiliones
- Harvestmen & Daddy-Long-Legs
- Prosoma & opisthosoma fused (no pedicel)
- Small bodies but very long legs
- Predators or scavengers
- 1 Pair of eyes
- Reduced chelicerae
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Harvestman, Hadrobunus sp.?; KY
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Desert Harvestman, Eurybunus sp.; AZ
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Ornate Harvestman, Vonones sayi; KY
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Order Scorpiones
- Scorpions
- Abdomen divided into Mesosoma and "tail"
- Large pedipalps form pincers (chelae)
- Venomous stinger at end of tail
- Reduced chelicerae
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Northern? Scorpion, Paruroctonus boreus?; UT
See also labeled photo.
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Arizona Bark Scorpion, Centruroides sculpturatus, ventral side of dried specimen
See also labeled photo.
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Arizona Striped-tail Scorpion, Vaejovis spinigerus; AZ
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Coachella Valley Sand Scorpion, Paruroctonus mesaensis; carrying young.
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California Forest Scorpion, Uroctonus mordax; CA
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Order Pseudoscorpiones
- Pseudoscorpions
- Large pedipalps form pincers (chelae)
- Abdomen lacks elongated "tail" and stinger
- Size tiny; often phoretic on beetles
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Pseudoscorpion, whole mount microscope slide
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Pseudoscorpion; AZ
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Pseudoscorpion; AZ
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Order Solifugae or Solpugida
- Sunspiders or Windscorpions
- Very large forward-pointing chelicerae
- Appear to have 5 pairs of legs: the anterior pair is actually enlarged leg-like pedipalps used as feelers
- Fast-running predators
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Straight-faced Wind Scorpion, Eremobates sp.?, male; AZ
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Straight-faced Wind Scorpion, Eremobates sp.?, female; AZ
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Sun Spider, Eremocosta sp.?; dried specimen
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Order Amblypygi
- Tailless Whipscorpions
- Pedipalps with spikes but not jointed chelae
- Flattened body
- First pair of walking legs extremely long (at least several times length of other legs) and function as feelers
- Lack telson
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Sonoran Whipscorpion, Paraphrynus mexicanus (native to southern Arizona)
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Florida Whipscorpion, Phrynus marginemaculatus; FL
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African Whipspider, Damon variegatus
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Order Uropygi
- Whipscorpions or Vinegaroons
- Enlarged pedipalps but with reduced chelae
- Flattened body in most
- First pair of walking legs longer and slenderer than others, act as feelers
- Posterior end with a thin, straight telson that squirts acetic acid
- Short-tailed whipscorpions are small (<5 mm), tropical species with very short telson; sometimes placed in their own order, Schizomyida
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Philippine Vinegaroon, Minbosius manilanus
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Giant Vinegaroon, Mastigoproctus giganteus
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Short-tailed Whipscorpion, Schizomus floridanus, preserved specimen
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