On August 13, a reader sent us this picture of a mass of living worms on her driveway. The worms were wiggling and had a black dot at one end of each worm. She was concerned that the mass of worms could have been vomited up by one of her dogs, which had been exhibiting symptoms of illness, but we think these Fungus Gnat larvae (Sciaridae) came from the lawn.
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While the shiny mucal gloss on this mass may have caused her concern about the worms having been passed by her dogs, it’s actually the very thing that allowed this mass of larvae to move as one onto her driveway.
Although the adult Dark Wing Fungus Gnats (Sciaridae) live on the types of fungal growth that grow in overwatered lawns and potted plants, the larvae will sometimes move in a ‘slick’ of mucous secretions they emit for protection in order to find a drier place to pupate, especially after heavy rains.
The reader mentioned that her neighborhood was a new development without many trees, and perhaps new installations of lawns, or surrounded by farmland. Heavy watering or changes in drainage may create the overly damp environments these Sciaridae larvae seek to escape, although moving onto a blacktop driveway may prove to have been a little extreme. It’s not unlike earthworms emerging to the sidewalk once rain has saturated their environment.
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Had the individual larvae, or the little black adult gnats been found near a flowerbed or in potted plants, we might recommend a thin layer of sand across the top of the potting soil and attentiveness to drainage, making sure to remove any standing water. Fungus Gnats can attack the fine root fibers on houseplants and other plantings and prevent them from drawing the water they need to grow. Looking around the property to identify areas of standing water or damp plant litter mulch may identify other areas the Sciaridae larvae are developing.
It’s increasingly unlikely that these worms came from her dogs, unless a curious pup discovered the mass and nosed around in the interest of learning more!