Why are there so many worms after it rains?

SIOUX FALLS, S.D. (KELO) — The worms on pavement after a rain could be looking for love.

Research shared by multiple sources including Scientific American and the Earthworm Society of Britain, said earthworms may be emerging from the ground after a rain to look for a mate.

The water makes it easier to move around a find a mate, according to those sources and earthworm watch.

“The (worms) we see after the rain, those worms are following the water…,” said Matthew Grenier, the owner of Black Hills Worms in Rapid City.

Published research says that the theory that worms were escaping flooded burrows because of rain have given way to the mating, moving to a new location and other theories unrelated to escaping.

“Earthworms like water,” Grenier said. “The skin of the worm needs moisture…they do just fine in the water, they are not drowning.”

CoolGreenScience says that worms can travel faster through water than the under the ground which makes it easier to find mates or a new location.

Brad Herrick, an ecologist and research program manager at the UW–Madison Arboretum , explained in an educational video that worms can more easily move around on the moist surface. Earthworms can take oxygen from water through pores, Herrick said.

But worms share the sidewalk and pavement with other creatures and people. It’s risky to come to the surface to find a mate or new location.

Worms are vulnerable to birds who swoop them up as food, to the tires of vehicles and to human feet.

Grenier said that in general, the worms on the surface after a rain can return below ground. The public can place a worm on the soil or in the grass to help them out, he said.

The help could be productive because many worms are considered helpful to the soil.

South Dakota State University Extension describes three types of worms as litter dwellers, topsoil dwellers, and subsoil dwellers. Litter dwellers most often live in the forest, according to SDSU. “Topsoil and subsoil dwellers are typically found in gardens, agricultural fields, and grasslands, where they improve soil aeration, nutrient recycling, and water infiltration,” SDSU said in a published report called “The Seen and Unseen World of Invertebrates and Vegetables: The good, the bad, and the cute .”

Grenier’s descriptions are similar. The worms seen on the sidewalk and pavement after rain are the topsoil worms.

The subsoil worms live well below the surface and aren’t seen as often, he said.

The SDSU litter worms are described by Grenier as worms that live in leaves and other natural material. They would not be seen on sidewalks or pavement after a rain, he said.

The casings, or earthworm excrement, from the below soil worm dwellers are good for the soil, Greiner said.

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