This cactus has quite an arsenal of thorns. If you're in the area of the desert where Cholla's grow, be very careful where you go. Falling on one of these will be quite painful. There is a bird named a Cactus Wren who nests in these things. Good protection for it's young! Do you think the silly bird will come in for a soft, careful landing? It doesn't. It comes in almost full speed! It sticks out it's feet, closes up it wings and slams right into the thorns. Then it reaches down with it's beak and pulls the thorns out of it's feet. Weird. I like the lemon-lime color of the flowers, too.   Opuntia echinocarpa   (Cactus family)