A: I was not sure exactly what worms you were talking about until you brought in a sample in alcohol to the Nassau County Extension office. The worms found in your yard are called land planarians or black flatworms, Dolichoplana striata. They are tropical worms and their numbers will diminish somewhat in your yard during the winter. The worms have been found as far north as New Hampshire and west to California, they have even made it to Hawaii. We believe black flatworms were brought into the United States via the potting soil of tropical plants. When you consider the amount of plant material moved about the U.S. from tropical areas, it is easy to see how the flatworms could have become so widespread in nurseries and garden centers and then to our landscapes. Planarians have been known to hunt earthworms and insects but they cause no harm to humans or pets. The flatworms are really no more than a nuisance after they end up on the sidewalks and driveways (hardscapes). Once they are out of the soil the flatworms become dehydrated, which causes them to die. After the black flatworms are dead and dry, they are much easier to sweep off into the lawn or ornamental beds. When our weather dips into colder temperatures over several days the worms go deeper into the soil which means you will see less and less of them. This is one of nuisance creatures for which you need to simply grin and bear it.

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