It is actually a Three-Lined Potato Beetle as I discovered when I read Maine Organic Farmers and Gardeners Association Pest Report:
No. Those are not cucumber beetles. Potatoes, tomatoes and sometimes eggplants are attacked by this pest that only superficially looks like a cucumber beetle. This is the Three-Lined Potato Beetle. The adult of this pest is about the same size as a cucumber beetle but has a reddish head and a thorax with two dark spots. The wing covers are dark yellow with three black stripes.
For comparison, here is a photo of a Striped Cucumber Beetle from the University of Maine Cooperative Extension website: