09/2019 updated 09/16/2026
The Bombardier Beetle: A Challenge for Step-by-Step Evolution
The bombardier beetle possesses one of the most remarkable defensive systems in the animal kingdom. When threatened, it combines stored chemical precursors with specialized enzymes inside a reaction chamber, producing a rapid chemical reaction that ejects an irritating spray at approximately 212°F (100°C).¹
The system involves far more than simply mixing two chemicals. Research has identified hydroquinones and hydrogen peroxide in the chemical system, together with enzymes including catalases and peroxidases that facilitate the reactions.² The beetle also possesses specialized glands, reservoirs, ducts, valves, muscles, and a reaction chamber that allow the chemicals to be stored safely, mixed when needed, and expelled toward an attacker.³
This raises an interesting evolutionary question:
How did this integrated defensive system develop through a step-by-step evolutionary process?
Dawkins and the Bombardier Beetle
Creationist Francis Hitching described the bombardier beetle by saying:
“The beetle squirts a mixture of hydroquinone and hydrogen peroxide into the face of the enemy. The two chemicals, when mixed together, literally explode.”
Richard Dawkins challenged this description in The Blind Watchmaker. Dawkins pointed out that merely mixing hydrogen peroxide and hydroquinone does not reproduce the beetle’s explosive reaction. Enzymatic catalysts are also involved.
On that particular point, Dawkins was correct. Hitching’s simplified description omitted an important part of the chemistry.
But does correcting that omission explain the evolutionary origin of the bombardier beetle’s entire defensive system?
No. It explains why Hitching’s description of the chemistry was incomplete. In fact, the additional enzymatic components reveal that the biological system is more complicated than a simple mixture of two chemicals.
Modern research confirms this complexity. A 2025 molecular study of Brachinus crepitans identified gland-specific catalases and peroxidases, enzymes associated with hydroquinone production, and a highly organized distribution of proteins throughout the beetle’s defensive glands.²
Chemicals That Were “Already Around”
Dawkins proposed that the ancestors of bombardier beetles utilized chemicals and biological components that already performed other functions and gradually recruited them into a defensive system.
This concept is known in evolutionary biology as co-option, in which an existing biological component acquires an additional or different function.
That is a legitimate evolutionary hypothesis, but it leads to another question:
What were the actual selectable intermediate stages that transformed those components into the integrated bombardier system we observe today?
Showing that catalase, peroxidase, quinones, glands, muscles, and ducts can exist independently does not by itself demonstrate the historical sequence by which they became coordinated into the modern mechanism.
Consider an analogy.
Suppose someone asks:
“How did a stereo system originate?”
The answer,
“Its amplifier, speakers, receiver, and power supply were components that already existed,”
identifies possible components, but it does not explain how those components became assembled, coordinated, and regulated into the functioning system.
Likewise, saying that bombardier beetle ancestors recruited chemicals and enzymes that were “already around” proposes a source for some of the components. It does not, by itself, reconstruct every stage through which the complete defensive apparatus arose.
The Integrated System
Research shows that the bombardier beetle’s defense involves multiple coordinated features, including:
- Chemical precursors: hydrogen peroxide and hydroquinones
- Enzymes: including catalases and peroxidases
- Secretory glands: producing and supplying the chemical components
- Reservoir structures: storing chemical precursors prior to discharge
- Muscular control: moving reactants through the system
- A reaction chamber: where the rapid chemical reaction occurs
- Valves and ducts: controlling movement and preventing the reaction from damaging the beetle
- An outlet system: directing the hot chemical spray toward a predator³
Detailed anatomical studies have even identified specialized structural features in the reaction chamber and resilin in areas subjected to substantial mechanical stress during discharge.³
This is therefore not merely a question of where hydrogen peroxide or hydroquinone came from. It is a question about the evolutionary history of an integrated chemical, enzymatic, anatomical, and regulatory system.
What Evolutionary Research Has Shown
It would be incorrect to say that scientists have offered no evolutionary explanation for the bombardier beetle.
Researchers have compared bombardier beetles with related beetles possessing other forms of chemical defense, investigated the anatomy of their defensive glands, studied the biosynthesis of their quinones, and examined molecular changes in enzymes associated with the explosive reaction.² ³ ⁴
For example, the 2025 molecular study reported evidence that bombardier beetle peroxidase genes underwent functional changes associated with the explosive secretion system.²
These discoveries provide potential pieces of an evolutionary history.
However, proposing precursor functions and identifying modifications of existing biological components is different from experimentally demonstrating the complete historical sequence by which the modern integrated system arose.
That distinction is the central issue.
The challenge is not merely to say that existing chemicals were recruited, or that related beetles possess simpler chemical defenses. The stronger question is:
Can the proposed evolutionary pathway identify biologically realistic, selectable intermediate stages connecting ancestral chemical defenses to the complete bombardier mechanism?
That requires explaining the coordinated development of the chemical precursors, enzymes, glands, reservoirs, valves, reaction chamber, protective structures, muscular control, and directional discharge mechanism.
The bombardier beetle therefore remains a fascinating case study in biological complexity and an important subject for examining exactly how far proposed evolutionary mechanisms can be experimentally demonstrated.
Sources
1. Aneshansley, D. J., Eisner, T., Widom, J. M., & Widom, B. “Biochemistry at 100°C: Explosive Secretory Discharge of Bombardier Beetles (Brachinus).” Science, 1969.
2. “Molecular basis of the explosive defence response in the bombardier beetle Brachinus crepitans.” 2025. This study used transcriptomic and proteomic analyses to identify catalases, peroxidases, hydroquinone-related enzymes, and molecular organization within the defensive glands.
3. “Functional anatomy of the explosive defensive system of bombardier beetles.” 2015. Comparative anatomical research describing secretory tissues, collecting ducts, muscular structures, reservoirs, valves, and reaction-chamber architecture.
4. “Biosynthetic origin of benzoquinones in the explosive discharge of the bombardier beetle Brachinus elongatulus.” 2020. Research examining the chemical precursors stored in the reservoir and their conversion during defensive discharge.
Richard Dawkins, The Blind Watchmaker, discussion of the bombardier beetle.
Michael Behe, Darwin’s Black Box, discussion of biochemical complexity and evolutionary explanations.
When these two ingredients are combined with an additional enzyme, the beetle can spray (with amazing accuracy) a toxic chemical that reaches burning hot temperatures of 2120 F.
How could this have developed through sequential steps if inert chemicals provided no benefit during sequential evolution? Such puzzles defy evolutionary models and predictions.
A creationist, Francis Hitching described the bombardier beetle’s defense system: “The beetle squirts a mixture of hydroquinone and hydrogen peroxide into the face of the enemy. The two chemicals, when mixed together, literally explode.”
Richard Dawkins within the Blind Watchmaker criticized this assertion. Dawkins explains that where Hitching describes the beetle’s defense system as a “a mixture of hydroquinone and hydrogen peroxide…(which) when mixed together, literally explode.” Dawkins points out that when he personally did the experiment and mixed together these two chemicals (as described by Hitching), with enough chemicals to represent 50 bombardier beetles, nothing happened—no explosion.
Dawkins correctly points out that an additional catalyst is required for the explosion: an enzyme not mentions by Hitching. Therefore, Dawkins concludes victoriously, the beetle could have evolved in a Darwinian step by step method by sequentially adding inert ingredients over generations (although providing no benefit to the organism) until ultimately all three complete with all the required apparatus had randomly formed, then, and only then, the beetle could use the chemicals as a weapon.
Then Dawkins victoriously reiterates: “the two chemicals together ‘literally explode’, is quite simply, false, though it is regularly repeated throughout creationist literature.”
Dawkins, Richard “The Blind Watchmaker” page 36
So Hitching failed (or perhaps chose to emit for simplicity to the reader) the enzyme that is also required for combustion. Therefore, such an omission debunks the point? Of course not! Rather, this adds more to Hitching’s point by adding yet an additional layer of complexity to the process: not just two chemicals but an additional enzyme is required for combustion!
Dawkins explains that “the beetle’s ancestors simply pressed into different service chemicals that already happened to be around. That is how evolution works.”
When Hitching neglected to include the enzyme catalyst in his example, then Dawkins pointing out this omission: does nothing to explain how the beetle’s defense system came about via evolution. What Dawkins is essentially stating is evolution uses complex molecular machines and functions that are merely “already around”. This is laughable.
“As an analogy:
Question to Richard Dawkins: “How is a stereo system made?”
Dawkins answers: “By plugging in (things ‘already around’) a receiver, amplifier, CD player, and tape deck.”
Such “answers” provide zero insight as to how the complex functioning systems of the receiver, CD player, or the speakers came about from the start.
This conclusion does not explain the arrival of the beetles defense apparatus, chemicals, or function.
Although such stories seem to be fit for evolutionary literature.”
Derived from Dr. Behe, Michael “Darwin’s Black Box”
Such descriptions evolutionary explanations are used to describe all complexity in living function including the origins and function of the human eye or the blood clotting cascade. The most we can derive from such simplistic narratives is perhaps Darwinian evolution may have occurred.
Survey says: mountains of data but actual answers are no where to be found.
http://www.talkorigins.org/faqs/bombardier.html
