Arizona Bark ScorpionCited field reference
Biology

Venom: what is in it and what it does

Direct answer

Bark scorpion venom is a mixture of small peptide neurotoxins that target voltage-gated sodium channels in nerve cells. Alpha-toxins jam the channel open so the nerve stays depolarized; beta-toxins lower the threshold so the nerve fires on its own.[1] The result is uncontrolled firing of sensory, motor, and autonomic nerves: burning pain, jerking, roving eyes, drooling, and a racing heart.[1][2]

By Devon "The Scorpion Guy" at ArizonaBarkScorpion.orgPublished 2026-09-12Last reviewed 2026-09-12Editorial policy

What is scorpion venom made of?

Scorpion venoms are complex mixtures of peptides, enzymes, salts, and small molecules. In Centruroides, the components that matter clinically are short peptide toxins, roughly 60 to 70 amino acids long, stabilized by disulfide bonds, that bind voltage-gated sodium channels (NaV) on nerve membranes.[1] These channels are the molecular switches nerves use to generate electrical impulses, which is why the toxins are so effective at causing pain and involuntary activity.

How do alpha- and beta-toxins differ?

How bark scorpion toxins act on nerve sodium channels Three panels. Normal: a sodium channel opens briefly then inactivates. Alpha-toxin: the channel is held open, sodium keeps entering, the nerve stays depolarized. Beta-toxin: the channel opens at a weaker stimulus, so the nerve fires spontaneously. Normal channel Opens, then inactivates in ~1 ms Alpha-toxin (α-NaTx) binds site 3 Inactivation blocked: held open Beta-toxin (β-NaTx) binds site 4 Threshold lowered: fires on its own Conceptual schematic after He et al. 2025 (Int J Biol Sci). Not a molecular structure.
Figure 1. Conceptual schematic of the two toxin classes, after He et al. 2025.[1] Not a molecular structure.

Alpha-toxins bind near the channel's domain IV voltage sensor (receptor site 3) and block fast inactivation, the step that normally shuts the channel about a millisecond after it opens. The channel stays open, sodium keeps entering, and the nerve stays abnormally depolarized: sustained burning pain and repetitive firing.[1]

Beta-toxins bind the domain II voltage sensor (receptor site 4) and trap it in an activated position, so the channel opens in response to much weaker stimuli than normal. Nerves fire spontaneously and repetitively even without a strong trigger.[1] Centruroides venoms are especially rich in beta-toxins, which is part of why their stings produce the involuntary muscle activity and autonomic storm that other scorpion stings do not.[1]

Why does the sting cause those particular symptoms?

Because the toxins do not discriminate among nerve types. Sensory nerves misfiring produce the pain, tingling, and numbness. Motor nerves misfiring produce jerking and restlessness. Cranial nerves misfiring produce roving eye movements and trouble swallowing. Autonomic nerves misfiring produce drooling, sweating, fast heart rate, and high blood pressure.[1][2] This is also why antihistamines and epinephrine do not help: there is no allergic mechanism to block.[2]

How does it rank among US scorpions?

The 2026 JIPM review classifies the bark scorpion's sting as a "Class III" sting, capable of life-threatening systemic effects, a category no other US species reaches for a healthy adult.[3] Most other Arizona scorpions produce pain comparable to a bee sting.[4]

Why do scientists study it?

Sodium-channel toxins are precision tools for mapping how pain works. The 2025 review in the International Journal of Biological Sciences uses scorpion toxins to dissect the channel subtypes involved in pain signaling, with an eye toward new analgesics.[1] The southern grasshopper mouse, which preys on bark scorpions, has evolved a sodium-channel variant that turns the venom into a painkiller, a discovery that came from studying this exact predator-prey pair (see diet and predators).[5]

What is not knownThe full toxin inventory of C. sculpturatus venom is still being characterized, and individual variation in venom composition between populations has not been mapped.[1]
Cite this pageDevon "The Scorpion Guy" at ArizonaBarkScorpion.org. "Arizona Bark Scorpion Venom: What Is in It and How It Works." 2026-09-12. https://arizonabarkscorpion.org/venom/

Related

Sources for this page

  1. He Y, et al. Deciphering Scorpion Toxin-Induced Pain. International Journal of Biological Sciences 21(7):2921-2934, 2025. www.ijbs.com/v21p2921.pdfTier 1
  2. Ruha A-M, MD. What You Need to Know About Scorpion Stings. University of Arizona Health Sciences, June 12, 2023. healthsciences.arizona.edu/news/blog/what-you-need-know-about-scorpion-stingsTier 2
  3. Agnew J, Bowers K, Bundy S, Romero A. Distribution, biology, and management of medically relevant bark scorpions, with emphasis on Centruroides sculpturatus. Journal of Integrated Pest Management 17(1), 2026. academic.oup.com/jipm/article/17/1/pmag029/8724371Tier 1
  4. Gouge DH, Li S, Bibbs C, Nair S. Scorpions of the Desert Southwest United States. University of Arizona Cooperative Extension, publication AZ1768, 2018. acis.cals.arizona.edu/community-ipm/community-ipm-output/publications/publications-view/scorpions-of-the-desert-southwest-united-statesTier 1
  5. Wikipedia contributors. Arizona bark scorpion. Wikipedia (cross-reference; consult its citations for primary sources). en.wikipedia.org/wiki/Arizona_bark_scorpionTier 2