From GERALD LEGG
Like any other organism, the design of daddy-longlegs is influenced
by fundamental physics.
If you are small and need very long legs to move about your environment
then it is no use having your body balanced on the tops of the limbs.
Humans have also found this out, the hard way, in the designs of many-wheeled
vehicles. If you were to be balanced like this then up goes the centre of
gravity and over you go.
It is a wonder the ‘Martians’ in Wells’s War of the Worlds driving around
in their tall machines were never toppled before they eventually succumbed
to the common cold.
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Nature has beaten us again – this time in the design of underslung suspensions.
For stability, the body (or chassis) is mounted near the ground, attached
to long, bent limbs (or spring mountings and springs).
Not only does physics necessitate this stable design, but also the number
of limbs you have. Most arthropods have five, six or eight pairs of walking
legs simply because this is the optimum range of numbers of legs for ‘normal’
walking in animals of their size. Many species, in fact, use fewer legs
to move when they start running since it is physically more efficient to
do so.
Gerald Legg Booth Museum of Natural History Brighton
