Chayote, a kind of squash, is popular in South American cooking and can be found at many grocery stores. Slideshow: More Latin American Recipes
Cut the squash in half lengthwise then scoop out the seed with a spoon. Cut the squash into 1/4-inch slices.
In a medium pot, cook the squash in boiling salted water until just tender, about 8 minutes. Drain and let cool.
Zest 1 orange and place the zest in a salad bowl. Using a sharp knife, peel the oranges, removing all of the bitter white pith. Working over a bowl, cut in between the membranes to release the sections. Squeeze the juice from the membranes into the bowl and discard. Stir in the cilantro, olive oil, vinegar, 1 teaspoon of salt and 1/2 teaspoon of pepper. Toss the cooled chayote and arugula with the fruit and dressing. Season with salt and pepper to taste, then serve.