Arthropods - Legs but no Backbone
Fortunately, you will probably never have to deal with the beastie in the photograph on the left! This is the Giant Weta, from New Zealand - one of the largest arthropods in the world.
Arthropod simply means 'jointed limbs' and invertebrate (without a backbone) animals with legs are often referred to as arthropods so that it includes all 'creepy-crawlies', not just insects, but spiders, centipedes, woodlice etc.
There are literally millions of arthropod species in the world and only very few cause problems to you and your plants, so it is important to recognise the different types and ESPECIALLY the DAMAGE they CAUSE - because many, like spiders and ground beetles, are valuable helpers in the garden, and the majority are harmless or, at the very worst, not worth worrying about!