What Are the Hard Shell Bugs in My Swimming Pool?

Characteristics

• Water beetles have characteristics that allow them to live in the water. Their streamlined bodies let them glide in the water, and their legs have fine hairs that help them push themselves through the water. Their wings store air that they can breathe when underwater.

Types

• Various types of hard-shelled water beetles may live in your swimming pool. The water scavenger beetle measures about 1 1/2 inches in length and is greenish black in color. The whirligig beetle is smaller at about 3/8-inch long. It has a shiny black shell with yellow legs. The predaceous diving beetle measures between 1/4 to 1 3/16 inches long, with a black body and a yellow line going around the top of its body. The small crawling water beetle measures 1/8-inch long and is yellow with black circular markings all over its wing covers.

Behavior

• Most water beetles swim by moving their legs alternately in the water. The predaceous diving beetle moves its legs together when swimming. Many water beetles can fly, and they find light to be attractive. They may feed on plant materials, other insects or even fish. They may hurt you if you handle them. For example, the water scavenger beetle can stab you with the sharp keel on the underside of its body. The predaceous diving beetle has sharp jaws that can inject a poison.

Control

• Although water beetles may fly, they don't survive very long without water. You can kill water beetles by taking them out of the water with a long-handled pool net, keeping them dry in a sealed plastic bag and discarding their bodies. You don't have to use a chemical to kill water beetles. You can use a spray insecticide to kill water beetles when they gather around lights, but insecticides in pool water may harm swimmers.