I have always wondered why animals use terrestrial locomotion?  Why don't they just disappear and then reappear wherever they want to be?
It is definitely an interesting topic! I believe the way the body is supported by the legs is an important part. 
Yes, my appendages are certainly helpful in giving me an upright posture.  However slime molds also move, and they don't have legs.  They must be teleporting, right?
I find it interesting that certain animals have different posture's depending on the situation
Yes, i agree. I have two legs, so i understand my method of locomotion.  But what about the Springtail, which hurls itself where it wants to go by using it's tail like Furcula?
I have never heard of Furcula. Do you have more information on that?
Not right now, but that's all the hard questions.  I also like the praying mantis: it has four legs, two forearms, aqnd wings.  How's that for a multi modal system of terrestrial locomotion?
Mantis
Mantises are an order (Mantodea) of insects that contains over 2,400 species in about 430 genera in 15 families. The largest family is the Mantidae ("mantids"). Mantises are distributed worldwide in temperate and tropical habitats. They have triangular heads with bulging eyes supported on flexible necks. Their elongated bodies may or may not have wings, but all Mantodea have forelegs that are greatly enlarged and adapted for catching and gripping prey; their upright posture, while remaining stationary with forearms folded, has led to the
of terrestrial locomotion, it is the basic form of locomotion of two major groups with many terrestrial members, the vertebrates and the arthropods. Important aspects of legged locomotion are posture (the way the body is supported by the legs), the number of legs, and the functional structure of the leg and foot. There are also many gaits, ways of moving the legs to locomote, such as walking, running, or jumping.
Legged locomotion Posture.
Appendages can be used for movement in a lot of ways: