This is a photograph of a Harlequin bug. They are a pest and will usually show up when you leave your spring vegetables too long in the summer garden.
I left my broccoli and kale deep into the spring going into the summer vegetable in order to let them go to seed for next year. As a result, I had a huge infestation of these harlequin bugs. Once the broccoli and kale were cut down, however, they left in fairly short order. They stayed around for a little bit of time preferring to roost in the flowering stalks of my corn, but it did not appear that they were doing any damage to my summer vegetables. They have since left.
In the Texas Bug Book, Howard Garrett states that these bugs feed on spring vegetables and can cause light splotches, shriveling, and deformity on their leaves. He advises that the best way to avoid these bugs is to plant your spring vegetables early in the Spring or in the Fall, and take the spring vegetables out once it gets hot.
Here is a photograph of their eggs. They like to lay these on the underside of the leaves of spring vegetables.