Just as Japanese beetles were becoming bothersome, destroying every flower of the purple Passionflower vine (Passiflora incarnata, below), they have vanished, though certainly not due to any action on my part. My displeasure counts for little in this garden. 
I suspect that the beetles’ movement into the next phase of their lifecycle is determined by the number of days since they have emerged from the ground, and without a doubt has nothing to do with running out of foliage or flora to dine on. Several buds remain on the passionflower, and the vine continues to grow and flower into late summer.
The yellow flowered passionflower (Passiflora lutea, below) is just beginning to bloom, and of course it will not be bothered by the beetles. With my post surgery gimpiness, there was more danger in reaching the small yellow flowers, but I managed to grasp woody hydrangea branches to steady myself as I inched along damp boulders at the koi pond’s edge. 
Yes, I understand that this is only a garden, and my health is immeasurably more important. But, I’m getting along much better than expected a week after surgery, and after a downpour this afternoon I was anxious to explore.
The yellow passionflower is planted at the far side of the koi pond so that it is reached only by pushing through Oakleaf (Hydrangea quercifolia) and panicled hydrangeas (H. paniculata), Japanese irises (Iris ensata), and a variety of weeds that have infiltrated the pond’s edge this summer. The vine has grown up through the hydrangea into an overhanging Okame cherry, with stems that droop back down onto the hydrangeas. While vigorous in growth, foliage of the yellow passionflower is not dense and it does no harm to supporting shrubs.
The panicled hydrangea that I clung to for dear life is a seedling of the nearby ‘Tardiva’ (Hydrangea paniculata ‘Tardiva’). While ‘Tardiva’ has been eclipsed in popularity by newer introductions, it remains a fine shrub with long lasting white blooms. Flowers of the seedling are larger, and stand more erect, and it is likely that some day into the future when I am able, this volunteer will be chopped out, so that it will not live to maturity.
Ramblin' through Dave's Garden 
We are several miles north of you and they are still dining on my plants…ravaging roses, J. Maples and some perennials. I pull off multi orgying groups and crush them with glee…I know the end is nigh. I’ve got a peegee hydrangea as a standard and have gleaned several plants from it to enjoy throughout the yard. It is the only hydrangea that I see being pollinated and the only one I’ve gotten volunteers from…go figure as I thought they were sterile. Always enjoy your posts!
Seedlings of Tardiva have a pesky habit of growing beneath neighboring shrubs so that once they appear the woody stems are well rooted and difficult to pull. Too often I make the temporary fix of breaking or pruning the stem so that it comes back next year with more vigor. Because this seedling hydrangea has grown through branches of a wide spreading Oakleaf hydrangea, it has developed a strong single trunk that would be excellent as a standard if it was not in the wrong place. There’s so much growing around it that it is impossible to transplant it, so eventually it will be cut off, and maybe some day I’ll chop out the roots.
LOL i have the same problem with black walnuts