Designed for defence

The Bombardier Beetle's chemical weapon

It has taken a brilliant mind to design the amazingly complex defence mechanism of the tiny bombardier beetle. When attacked, this little warrior fires a cloud of boiling-hot noxious gases into the face of his assailant and, while it beats a hasty retreat, he scuttles away to a safe place. Whilst the construction of this insect cannon and the chemistry of the explosion have been known for some years, new research has uncovered some more fascinating facts.

Many features of design in the Bombardier beetle are well known (Aneshansley et al. 1969) and have often been described by creationists to demonstrate the wonderful design of the animal and the absurdity of clinging on to evolutionary explanations. Only the essential outline is summarised here.

The defense mechanism includes: the hydraquinone and hydrogen peroxide reactants, the oxidative enzymes, the two reservoirs which contain the mixture of chemicals, the thin walls of these reservoirs which permit muscular control, the thick-walled reaction chamber (providing robustness), and the valve which seals the reservoirs from the reaction chamber. When they contact the enzymes in the reaction chamber, the chemicals react quickly, generating so much heat that there is an explosion and the reaction products pass through the abdominal tip which, like a revolvable turret, is used to aim the spray. As a striking example of complex design, this defence mechanism has few rivals. Evolutionary explanations are lacking as to how so many exquisite and critical features could have been assembled to make the functioning defence mechanism.

           GG         GGG           +-----------------+
          GGGGG     GGGGGG          |                 |
          GGGGGG   GGGGGG           |  Hydroquinone   |
          GGGGGGGGGGGGG             |                 |   RESERVOIR
           GGGGGGGGG================ -->  + Hydrogen  |
           GGGGGGG                  |       Peroxide  |
         GGGGGGGG                   |                 |
       GGGGGGG      GLANDS          |        |        |
        GGG                         +------+ V +------+
                                           |   |
                                 OOOOOOOOOO|   |OOOOOOOOOO
                                O                         O
                                O -->                     O
                                 O   Enzymes             O
                                  OO -->               OO
                                    OO               OO
                                      OO           OO
                                        OOO  |  OOO
                                           O | O
                                           O | O
                                             V
                                Oxygen, quinone and water

Recent research has found that, in some species of the beetle, the spray is emitted, not as a continuous stream but as a pulsed jet. Individual discharges have been observed with 2-12 pulses, at rates of 368-735 pulses per second. Analysis of the internal structure of the beetle suggests that the valve action to produce the pulsed effect is virtually automatic. Further details of the mechanisms involved are contained in the research report (Dean et al. 1990).

Pulsed delivery systems have several advantages over non-pulsed systems.

High discharge velocities are not dependent on musculature control. Muscles merely introduce materials to the reaction chamber and have no direct role in expulsion. The high pressures needed to produce high velocities (with a mean of 11.6 metres per second) are the result of the explosive reaction.
Control of the duration and direction of the spray is facilitated. Propulsion is not by muscles, so the reaction can be maintained as long as the reagents are available. The beetle is free to put its energies into directing the spray and adjusting it to match the threat.
There are possible benefits from reducing the danger of thermal denaturation of the enzymes. Cool reagents are moved into the reaction chamber, permitting a lower average temperature and promoting stability of the enzymes. This in turn may increase the safety factor for the beetle.

An analogue suggested by the research team is the pulsed propulsion mechanism of the V-1 buzz bombs of World War II. The V-1 engines were designed to maintain control over the reaction, but at the expense of discontinuous thrust. That is, they were sub-optimal. This problem does not arise for the beetle: the pulsed mechanism produces an effective deterrent with (a) minimum muscular force, (b) good control of direction and duration, and (c) a high discharge velocity.

The living world is full of surprises. We find creativity, ingenuity, craftsmanship, beauty and aesthetic appeal, and technical excellence which can only be described with superlatives! The Christian's joy in discovery is intensely personal, for this is the handiwork of our God! The works of his hands declare his glory. The evolutionist will generally deny the Creator, but will often make some acknowledgement of perfection in the living world. In this case, the research team conclude that in the context of its end use, the defence mechanism of the beetle cannot be improved: `For this purpose, the pulsed mechanism is ideal'.

David J. Tyler (1994)

References:

Aneshansley, D.J., Eisner, T., Widom, J.M. and Widom, B. 1969. Biochemistry at 100C: explosive secretory discharge of bombardier beetles (Brachinus). Science. 165, 61-63.

Dean, J., Aneshansley, D.J., Edgerton, H.E. and Eisner, T. 1990. Defensive spray of the Bombardier Beetle: a biological pulse jet. Science. 248(8 June), 1219-1221.

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