Yellow Spotted Water Beetle

Thermonectus Marmoratus

Fascinating Facts

Physical Characteristics

These beetles range from 14-15mm in length. They are characterized by having a black carapace covered with bright yellow spots. Their streamline body aids in swimming through the water. Males have a suction disk on their forelegs.


Yellow Spotted Water Beetles live in ponds and lakes. When their water source dries up they will fly to a new one. They are found in extreme Southern California, Arizona, New Mexico, Texas, and Mexico, requiring at least a temporary water source.

In the wild, these beetles are useful because they eat other invertebrates including mosquito larvae and pupae. At the zoo, they eat dead organisms found on the surface film or the bottom.

Social Behavior

They are proficient swimmers using their powerful hind limbs to propel them through the water. Having functional wings they are able to travel to other areas when the pond they inhabit dries up. They share these ponds with other larger predators such as the Giant Water Bug (Abedus americanus) and the Ferocious Water Bug (Abedus herberti).

Status In The Wild

The Yellow spotted water beetle is common and not endangered.


The yellow spotted water beetle can be found at the Insect Zoo.

Animals & Exhibits