What Is the Difference Between Venomous and Poisonous?

Which are more dangerous: venoms or poisons?

The black widow spider is venomous.
The black widow spider is venomous. Shenrich91/Wikimedia Commons

The terms venomous and poisonous are adjectives applied to various animals that are often used interchangeably, but the words have different meanings. Both refer to the presence of toxic substances and their dangers to humans and other creatures, but the differences between the two are based on how the toxin is delivered to the victim: actively or passively.

Venomous Organisms

A venom is a secretion that an animal produces in a gland designed for the task.

It is actively introduced into another animal by means of a specialized apparatus. Venomous organisms use a wide variety of tools to inject venom into their victims: barbs, beaks, fangs or modified teeth, harpoons, nematocysts (found in jellyfish tentacles), pincers, proboscises, spines, sprays, spurs, and stingers.

Animal venoms are generally a mix of protein and peptides, and their precise chemical makeup to a large extent depends on the purpose of the venom. Venoms are either used for defense against another creature, or they are used for hunting prey, as food or as an incubator host. Venoms evolved for defense are principally streamlined to create immediate, localized pain to make the other animal go away. The chemistry of venoms for hunting prey, on the other hand, is highly variable, having been evolved specifically to kill, incapacitate, or break down the victim's own chemistry to make it easily edible.

If cornered, many hunters use their venom for defense.

Glands and Hypodermic Needles

The gland where venoms are stored have a ready supply of venom and a muscular arrangement to permit ejection of the poison, which may affect both the rapidity and degree of envenomation. The reaction in the victim is principally determined by the chemistry, potency, and volume of the venom.

Most animal venoms are ineffectual if the venom is merely placed on the skin or even ingested: venom requires a wound to deliver its molecules to its victims. One sophisticated apparatus known in the animal world is the hypodermic syringe-style mechanism of ants, bees, and wasps: in fact, inventor Alexander Wood is said to have modeled his syringe on bee sting mechanisms.

Some Venomous Arthropods

Venomous insects occur in three groups: true bugs (order Hemiptera), butterflies and moths (order Lepidoptera), and ants, bees, and wasps (order Hymenoptera).

Poisonous Organisms

Poisonous organisms, on the other hand, do not deliver their toxins directly; they are induced in others passively. Their entire body, or large parts of it, may contain the poisonous substance, and the poison is often created by the animal's specialized diet.

Unlike venoms, poisons are contact toxins, which are harmful when eaten or touched. Humans and other creatures can suffer when they come into direct contact with or inhale airborne material such as urticating (stinging nettle-like) hairs, wing scales, molted animal parts, feces, silk, or other secretions.

Poisonous secretions are almost always defensive in nature. Those that aren't defensive are simple allergens that have nothing to do with defense. Many such occurrences happen after the animal is long dead. The defensive contact chemicals produced by these poisonous insects may include severe local pain, local swelling, swelling of the lymph nodes, headache, shock-like symptoms and convulsions, as well as dermatitis, urticating rashes, and upper respiratory tract complications.

Some Poisonous Arthropods

Poisonous insects include members of quite a few groups: butterflies and moths (order Lepidoptera), true bugs (order Hemiptera), beetles (order Coleoptera), grasshoppers (order Orthoptera), and possibly others.

  • Stinging caterpillars use barbed spines or hairs as a defensive.
  • Blister beetle bodies produce a caustic chemical when they are threatened.
  • Monarch butterflies gain a defensive flavor by eating milkweeds, and birds that eat them only eat one.
  • Heliconius butterflies, many of which have similar defensive poisons in their system.
  • Cinnabar moths feed on poisonous ragworts and inherit the poison.
  • Lygaeid bugs feed on milkweed and oleander.

Which Are More Dangerous?

Venomous black widow spider bites, snake bites, and jellyfish stings certainly sound more dangerous than contact poisons, but in fact, in terms of worldwide exposure, the more dangerous of the two is undoubtedly animal poisons, since they don't require the animal to take an active role in the toxin delivery system, or in cases even be present or alive to do their damage.


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Hadley, Debbie. "What Is the Difference Between Venomous and Poisonous?" ThoughtCo, May. 4, 2018, thoughtco.com/venomous-vs-poisonous-1968412. Hadley, Debbie. (2018, May 4). What Is the Difference Between Venomous and Poisonous? Retrieved from https://www.thoughtco.com/venomous-vs-poisonous-1968412 Hadley, Debbie. "What Is the Difference Between Venomous and Poisonous?" ThoughtCo. https://www.thoughtco.com/venomous-vs-poisonous-1968412 (accessed May 26, 2018).