Used to be called Galerucella beetles until a recent taxonomic change. These eggs are minute. This is a section of a purple loosestrife leaf on which there were laid several clusters of eggs. The squiggly black stuff on top is insect poop, placed there in an attempt to ward off predators (though it usually doesn't work).

These beetles were introduced to control the spread of purple loosestrife. They were released at various sites about 10 years ago, with the idea that they'd spread outward from these drop-off sites. And they have. I've found them in areas far from where any were released. They are doing an amazing job of controlling loosestrife, and in locations where loosestrife was once abundant it is either absent or severely reduced. Of course, there are still locations where the purple loosestrife is widespread, and I have to say that I find it a beautiful plant, and one that feeds an enormous number of butterflies and other insects who nectar on it.