THE EXCEPTION PROVES THE RULE
Ever wonder why they say the exception proves the rule? I mean if it is the exception then how it can prove the rule? Well, here is an interesting demonstration of that principle in action.
There are many examples of mutually beneficial relationships between different species. One such relationship exists between certain Acacia plants and the ants that live among the Acacia thorns.
The plant provides shelter and food to the ants. The ants in return ruthlessly attack anything that moves, thereby eliminating potential threats to the plants from other insects. The rule in this case would be that ants know the difference between ant and non-ant.
The exception is the lowly squash bug, which moves among the ants with impunity, munching happily on the Acacia's succulent leaf tissues. Scientists at the University of Colorado wanted to know why the ants didn't attack the squash bugs like they did everything else.
What they found was that the squash bug smells like an ant. So when ants go past a squash bug they think it is just another ant. When the squash bugs were washed in a chemical solvent — removing the chemicals that made them smell like an ant — the ants immediately swarmed them.
By demonstrating how the squash bug gets past the ants' defenses, the exception proves the rule that ants excrete specific chemicals that establish their antness to other ants.
From the acacia plant's perspective, the lesson learned is a little different: Nothing is perfect. Or a as friend of mine likes to say, "Where there's a need, there's a way."
December 14, 2009
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