These are the leaf-eating beetles introduced over a decade ago, to control purple loosestrife. They have spread far and wide and it is not uncommon to find them in most areas where loosestrife grows. They are doing an amazing job, and most people have noticed the big reduction in purple loosestrife over time. There are still many places where the plants flower, and who knows if it will ever be eradicated, but it certainly seems to be under control. On the flip side, many insects, including many butterflies, nectar heavily on the beautiful purple flowers.