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Defense and Attack Strategies and Mechanisms in Biology 355

the vegetation and clamp on to the leaves with their mandibles. They stay there immobile until the
next morning. The ants are thus likely to be eaten by passing sheep, thus completing the life cycle of
the parasite. Although the parasite is obviously far more complex than a computer chip, the change
in the ant’s behavior is minimal: the interaction of the insect’s temperature response with its
response to gravity.

13.5.3 Pheromones

The chemical substances released by animals to influence physiology or behavior of other members
of the same species. One use of pheromones, at the most elemental level, could be to mark target
individuals and then release bees to attack them. This would result in forcing them to exit an area or
abandon resistance (Alexander et al., 1996).
Lima beans (Phaseolus lunatus) infested with spider mites release chemicals that attract preda-
tory mites that then prey on the spider mites. The uninfected plants downwind also attract predatory
mites. Jasmonic acid sprayed onto tomato plants may regulate volatiles that attract parasitoid
wasps that prey on caterpillars feeding on the tomato plants. Such indirect defenses may be
even more complex. This may then be why some plants house and feed the predators as has
happened in ant plants. The ants can be considered to be an induced biotic defense because the
number of ants that patrol the leaves increases severalfold as a result of attraction by volatiles
emitted from the damaged tissue when a herbivore chews a leaf. The ants are acting as a Praetorian
body guard.

13.6 ELASTIC MECHANISMS

Human technology used elastic mechanisms as power amplification of human or animal energy to
launch arrows and other projectiles; this approach is used in nature but man has replaced elastic
mechanisms with explosives.
The ability to escape quickly from a predator is vital for most prey,while predators have obvious
advantages if they are able to outrun fast prey and overpower it using even faster weapons.
The speed of running, jumping, predatory strikes, etc. is generally correlated with the animal’s
size. In order to achieve velocities comparable to those of larger animals, small ones such as
most arthropods have to rely on very high accelerations (Alexander and Bennet-Clark, 1977).
Therefore, in many insects, the speed of action reaches or even surpasses the velocity limitations
inherent in muscle contraction. Irrespective of phylogenetic relationships, convergent evolution has
resulted in special mechanical designs (e.g., springs or catapults) that overcome the constraints of
muscle action in many arthropods (Bennet-Clark and Lucey, 1967).
In addition to fast mechanics, both prey and predators rely on rapid neuronal and muscular
systems to initiate and control their swift escape or predatory actions. Among the ants, several
species employ particularly fast mandible strikes in order to catch swift prey or to defend
themselves. This so-called trap-jaw mechanism (a mandible strike which far exceeds the speed
allowed for by muscular contraction) has evolved independently in three ant species (Gronenberg,
1996). These studies reveal that the fast strike results from energy storage in a catapult design, and
its control relies on fast neurones and on a high velocity trigger muscle.
In biological elastic mechanisms, strain energy is stored only when the spring mechanism is
in the position from which the energy will be released — its loaded configuration. This is in
contradistinction to most man-made systems, where the assumption of the loaded configuration
is also the means by which the energy is stored (e.g., drawing a bow). For instance, the locust
brings its legs into the jumping position, then loads the main jumping tendon using muscle power.
This probably makes the system safer and allows a lower safety factor in the strength of the
components (Bennet-Clark, 1975).