More than half of the Morning Glory leaves have these distinctive beetle-holes in them.
Well, this morning, one of the culprits was visible so I could research it and learn about it.
What's that bug says it is Charidotella sexpunctata, sometimes called a Gold Bug. Both the larvae and adults eat the leaves of Morning Glories.
Scarabogram gives more information online - a 1994 article by Louise Kulzer.
The golden tortoise beetle is a stunning, vibrant metallic gold color. It has a magical quality, not only because of the brilliance of its color, but also because the brilliance isn't permanent. Metriona can alter color within a short time period, turning from brilliant gold to a dull, spotty reddish color. The gold color also fades when the insect dies. What controls the color while the insect is alive is an intriguing question, but one for which I have no answer. [The gold color is caused by a thin layer of moisture between the cuticle and an inner layer of the elytra. Apparently the insect is able to voluntarily squeeze this layer, reducing its thickness and eliminating the gold color. This change also occurs involuntarily when the beetle is under moisture stress, and, of course, when it dies.
Tortoise beetles overwinter as adults. In the spring the adults begin to feed, mate, and lay eggs. The larvae emerge and feed through the summer, and pupate in late summer. Adults reportedly emerge in the early fall, feeding until the morning glory gives up the ghost for the current season, and then hunker down among plant debris for the winter. I've only seen tortoise beetles on morning glory, which, in my opinion, is poetic justice. I wonder, however, if in the spring they might use alternate food plants since it takes a while for morning glory to put out many leaves, concentrating as they do on getting those stems out there. Natural history observations would be welcome, fellow Scarabs. Remember as you pass vacant lots to look for morning glory and holes in leaves. And do take a minute to look underneath.
Thanks to What's That Bug and Louise Kulzer.