Every summer we have a strange problem with our lawn and it is covering more of our lawn every year. There are small mounds of dirt that look like earthworm castings and are about 4 - 5 inches across and maybe a couple of inches high. They give the lawn a bumpy look especially because no grass grows where there is a mound. Most do not have an entry hole. I never see anything flying above or coming from the mounds. We have sandy soil. I would love to fix this!