Wasps Around Grass Clippings

Wasps have purposes other than stinging humans.

One species of wasp, known as the grass carrier, uses grass clippings to make a nest. If the grass clippings have been added to a compost pile, the wasps feed on the fly larvae hatching in the decomposing matter. Fresh-cut grass clippings that have been subjected to falling tree fruit carry sugars that draw wasps. Some paper nest-building wasps make their homes underground.

Nest Building

This wasp is of the genus Isodontia. The female collects grass clippings and stuffs them in a hole or crack. The hole or crack can be in the siding of an outbuilding or home. She then hunts down 1 inch long tree crickets and carries them to the grass nest. After she's stockpiled enough food, she lays her eggs. When the eggs hatch into larvae, they feed on the crickets.

Hunting Prey

Composted grass clippings begin to rot and decay. This environment is preferred by the common house fly. The female lays her eggs in the grass clippings and the maggots feed on the rotten grass. Female wasps seek the flies when they are in the pupa stage of development. She drills a hole in the pupa casing and lays her eggs. The wasp larvae then feed on the fly maggots.

Eating Fruit Sugar

When ripe fruit falls from your trees, it can burst open when it hits the ground. Bursting fruit sprays the surrounding grass with juice. The sugary juice attracts the wasps. If you mow your lawn without picking up the fruit, the mower blade spreads the juicy fruits all over the clippings. After you rake the clippings into a pile, it's quite common to see a swarm of wasps buzzing around and landing on the clippings feeding on the sugar.

Aggressive Behavior

Avoid going near a pile of grass clippings if you notice a swarm of wasps frantically flying around it. It's possible that you've just covered the entrance to an underground burrow. Eventually the wasps will burrow beneath the clippings to get back to their nest. Remove yourself from the area at the first signs of aggression made by the wasps.

References

• Iowa State University Extension; Grass-carrier Wasp; August 31, 2010
• "Mackinac Island News"; Mackinac Island battles Flies with Army of Wasps; Karen Gould; June 26, 2010
• Danny Lipford; How to Deal with Wasps in Your Lawn; Julie Day
• University of Minnesota Extension; Wasp and Bee Control; Jeffrey Hagn et al; 2009