Venomous Arthropods

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Venomous Arthropods

• And Their Associated Problems

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Envenomization

• Can be divided up into 2 categories
• (1) Passive Envenomization
• (2) Active Envenomization

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Envenomization - Action of Venom

• Neurotoxin (black widow spider)
• Cytolytic, hemolytic (brown recluse spider)
• Hemorrhagic (moth larvae)
• Vesicating/blistering (blister beetles)

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Stingers

• (1) Honey Bee
• (2) Bald Faced Hornet
• (3) Paper Wasps
• (4) Yellow Jacket
• (5) Red Imported Fire Ant (Solenopsis invicta)
• (6) Scorpions

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Venomous Hymenoptera
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Red Imported Fire Ant
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Fire Ant Mounds
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Red Imported Fire Ants The pathognomic pustules
following a fire ant envenomation.
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Velvet Ants Cow Killers
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Scorpions

• Scorpions are easily distinguished from other
  arachnids by their large, well developed claws
  and distinct division of the abdomen into a broad
  preabdomen and narrow, tail-like postabdomen.
• All scorpions are venomous, but only about 25
  species worldwide possess venom of sufficient
  toxicity to kill humans
• The venoms with severe toxicity are usually
  neurotoxins.

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Bites

• (1) Spiders
• Black Widow
• Brown Recluse
• Hobo Spider
• (2) Centepedes

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SPIDERS
Fiddle
Hourglass
Tarantula
Brown Recluse
Black Widow
Hobo
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Latrodectus mactans (Black Widow)
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Loxosceles reclusa (Brown Recluse)
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Progression of Bite (3-10 days)
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Tegenaria agrestis (Hobo Spider or Aggressive
House Spider)
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Hobo Spider Bites
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Distribution of venomous spiders causing necrotic
ulceration - United States and Canada.
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Lycosa tarantula (Wolf Spider)

• Occur in Europe and not the U.S.
• Not a Tarantual!
• 1370 recorded biting humans.
• Tarantism
• Dance called the tarantella

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Tarantulas

• 840 described species
• Fangs larger than those of most venomous snakes.
• Old world species more venomous than new world
  species.
• Neurotoxic
• Most species are harmless!

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Centepedes

• Class Chilopoda
• 20 families and over 2500 species.
• 1-pair of legs per body segment.
• Most small, a few are 10 inches or longer.
• 1st pair of legs are modified fangs.

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Scolopendra gigantea
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Other Methods

• (1) Millipede
• (2) Blister Beetles
• (3) Bombardier Beetles
• (4) Caterpillars (Moths)

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Millipedes - Class Diplopoda

• Millipedes (2 legs/body segment) do not have
  biting mouthparts or fangs. Their medical
  importance comes from their ability to secrete an
  irritating defensive liquid from pores along
  their sides.
• Such secretions contain benzoquinones, aldehydes,
  hydrocyanic acid, and other substances.

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Blister Beetles

• Family Meliodae
• Cantharidin
• Livestock come in contact with blister beetles.
• Spanish Fly

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Bombardier Beetles

• Family Carabidae
• ½ inch long.
• Chemical defense
• 70 rapid shots
• 100C (212F)
• Southern California

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Bombardier Beetles
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• Venomous Insects - Lepidoptera
• Problems Caused by Adult Moths
• Dermatitis
• Respiratory Distress (Asthma)
• Lachrymal and blood-feeding
• Problems Caused by Larval Moths
• Dermatitis
• Stinging envenomization - allergy
• Hemorrhagic manifestations

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Larval Moths Known to Cause Problems to Humans

• Urticating or "stinging" spines and setae.
• Average sensitivity
• stinging sensations
• Extreme sensitivity
• Severe pain and allergic reactions.
• Cases are known of hospitalization
• Skin bleeding (poison spines containing an
  anticoagulant)

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Lonomia electra Costa Rican species
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Puss Caterpillars

• Megalopyge opercularis
• Florida Species
• long, silken, brownish hairs.
• short, poisonous spines.
• burning sensation, as painful as a bee sting.

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Puss caterpillars. The caterpillar at the left is
fully grown the one at right is still
developing, note the recently shed (and still
urticaceous) skin beside the larva.
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Saddleback Caterpillar Sibine stimulea
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The io moth Automeris io Costa Rica
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Clues for Diagnosing Arthropod Envenomizations
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