We have ladybugs every year around the yard, but, when we planted three river birch trees in the backyard, six or seven years ago, the number of ladybugs increased significantly. Turns out, aphids like river birch leaves and ladybug larvae like aphids. We had to compromise on the number of aphid we allowed. So, every afternoon, I would walk through the leaves and collect aphids in my hair. You ever try sleeping with aphids crawling around your scalp?