I love spiders and think they are some of the coolest, most varied, and the most intelligent of all creatures with an exoskeleton. My favorite one as far as intelligence goes is the trap-door spider. This spider burrows a hole and then drags a rock or similar object over the hole. There they wait until something comes near. Like all spiders, trap-doors have a very keen sense of touch that allows them to feel even the tiniest vibrations. They can then pick out and identify what made those vibrations as far as size, weight distribution, etc. Something walks by its home. The spider recognizes it as an insect of some sort. It creeps up the hole, pushes the rock up, and looks to see what it is. It then pounces, grabs the insect, and drags it into its hole where, unlike other spiders, is eaten on the spot. But where the spider's real intelligence is demonstrated is something like the following scenario; a human walks by accidentally kicking the rock and spraying dirt on the spider. The spider will close its eyes, tense up, and stay still until the vibrations cease. Then it shakes itself off, climbs up, and repairs the damage. This demonstrates a cognitive ability that was never before seen in such a creature. Because of these traits, the trap-door spider is one of the most efficient, successful, and intelligent creatures on the planet.