Insect Chemical Warfare

Video – Bombardier Beetle Spraying Predator With Acid:

If you are an insect, then you better watch out because odds are something out there wants to eat you. Whether it’s a lizard, bird, mouse, or even another insect, the life of a bug is always at risk from predators.

Bugs are always devising new strategies to survive, and evolution, being the genius engineer she is, has produced several species of bugs with unique defense mechanisms. Many species of bugs have mastered the art of chemical warfare through various defense mechanisms that make use of chemical substances or agents. Bugs use these defense mechanisms to avoid becoming some other animal’s lunch or dinner.

The range of these kinds of chemical defense techniques runs the gamut from eating noxious plants to have a bad taste to literally blasting predator faces with corrosive acid.


One of the most common forms of chemical defense in insects is aposematism. Aposematic insects feed on noxious plants then advertise their poisonous and inedible status to predators through their bright color displays. Predators that eat these brightly colored poisonous insects experience getting sick and so learn to stay away.

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One of the most well-known examples of this kind of defense system is monarch butterfly larvae. Monarch caterpillars feed almost exclusively on milkweed which builds up cardenolides in their body. These cardenolides produce a foul taste when eaten, thus disincentivizing predation. Monarch butterfly adult wings contain high concentrations of cardenolides in their wings to deter predators from moving on to their bodies.

Various species of animals have evolved to mimic aposematic color displays found in other species, a relatively common survival strategy known as Batesian mimicry. By mimicking aposematic colors animals can discourage predation.


Other species of insects utilize chemicals through venom that is injected into their prey, either through stingers, fangs, or some other type of sharp appendage. Quite a lot of insect species have some form of venom, though the vast majority of them are not potent enough to pose a serious threat to humans. Common insects that use some form of venom include bees, fire ants, wasps, spiders, and scorpions (although technically, the last two are not insects).

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Most insects use their venom primarily for hunting prey but some species have adapted their venom for explicitly defensive purposes. For example, worker ants of some species have powerful venom adapted for killing colony invaders such as rodents, reptiles, and other arthropods.

Acid & Odors

Other insect species have adapted chemical warfare in the form of squirting acid at predators. For example, stick bugs are capable of spraying a mildly noxious acidic substance up to two feet from special glands in their thorax. Also, the Bombardier Beetle is known for spraying corrosive formic acid when threatened. These acidic substances are rarely if ever fatal, but they are corrosive and irritating enough to get predators to abandon a potential meal.

Other bugs intentionally produce a foul-smelling chemical to ward off predators. For example, stink bugs excrete a smelly chemical from their stomach glands. Some species can spray this fluid up to 3 inches from their bodies.