As an educated Ask Fuzzy reader you don't need to be told that caterpillars are insects. Insects have six legs, ergo a caterpillar has six legs.
But then if you look at a caterpillar you'll most often see 16 legs. And then there's the leaf-mining moth caterpillar that doesn't seem to have any legs at all.
A clue is that caterpillars have two pairs of legs attached to the thorax (the section behind the head), while there may be as many as five pairs of other legs - "prolegs" - attached to the abdomen (behind the thorax).
Their "true" legs are segmented and have suckers or hooks at the ends, while their "prolegs" do not.
And, during metamorphosis, true legs are converted into adult legs while the prolegs disappear. The prolegs are digested to form new structures such as wings.
And still they look like legs.
To preserve our insect six-leg classification, we either have to define away these extra legs to say they're not really legs, or narrow the insect category to say "adult caterpillars have six legs".
This question points to a fundamental feature about how we understand the world. Are categories such as these real? Or are they products of the human mind with its craving for order in a chaotic cosmos?
Now we're diving into the ancient musings of philosophers such as Aristotle and Plato where we can never be entirely certain of whether a category is real or a human invention.
Whatever the case, we find it invaluable in daily life to be able to apply labels to things. Imagine, for example, the mess if could never agree on definitions in law or in the bureaucracy.
This person is employed but they are not employed. This company is Australian but it is not Australian. This thing is an insect but it is not an insect.
Our caterpillar-insect question is tricky because they can do something that we cannot.
Metamorphosis is a strange process because it entails a fundamental reconfiguration of its body. Prolegs become wings, and so on - as the term suggests, it morphs.
Driving this is the process of evolution which, for insects, means that transforming their bodies in this way offers them an advantage of some sort.
Perhaps it's better that we humans don't metamorphose. If you think kids growing out of their clothes is hard enough, imagine if they sprouted or lost limbs at various stages.
The Fuzzy Logic Science Show is at 11am Sundays on 2xx 98.3FM. Send your questions to AskFuzzy@Zoho.com; Podcast: FuzzyLogicOn2xx.Podbean.com
