[eli5] Why do insects have lots of legs while larger animals have 4 or 2? Also, why aren’t there any animals (that I know of) with 3 legs?

Question

[eli5] Why do insects have lots of legs while larger animals have 4 or 2? Also, why aren’t there any animals (that I know of) with 3 legs?

In: 381

Answer 1

Warm blooded animals have a better sense of balance than cold blooded animals. Balance works better if reflexes react at a predictable speed. A constant body temperature makes reflex speed somewhat constant. Gravity is constant so how fast you fall over won’t change with temperature. Some cold blooded animals like insects and spiders use extra legs for balance instead of relying on their brains for balance. They also tend to have a wide stance. Many reptiles also have a side stance.

A kangaroo can use its tail as an extra leg, but not while traveling fast (hopping).