The term 'eight-legged invertebrate' is a description of an ARACHNID, which is an eight-legged creature that does not have a backbone. Arachnids are a class of invertebrates, meaning they lack a backbone or spinal column. Examples of arachnids include spiders, scorpions, mites, and ticks. They are found in a variety of habitats, from deserts to forests, and can range in size from microscopic to several inches long.