Sunburst Diving Beetle Fact File

Thermonectus marmoratus








Wild Unknown

Captive 1-2 years




Conservation Status


Not Evaluated

The sunburst diving beetle is named for its colorful pattern of yellow and black across the back. This warns predators that they are equipped with a foul tasting fluid which they can use to get rid of predators.

They make their home in small ponds of water in desert and forest habitats.

Much of their time is spent in the water with the ability to trap an air bubble under the wings which allows them to remain underwater for longer periods. They tend to only leave the water to fly or lay eggs.

Sunburst diving beetles face a range of predators along with threats from pollution.

Learn more about these brilliant beetles by reading on below.


Their large rear legs are colored red and help to push them through the water. The legs have fringes which assist with floating in the water.

On either side of the body are three legs for a total of six. Protruding from the head are a pair of antennae.

Across their back the sunburst diving beetle is colored black with yellow spots patterning this background. These are considered warning colors to show predators that they have a foul tasting chemical they can use to fend off threats. The underside is colored orange or reddish-orange.

Sunburst diving beetles have a unique eye while in their larval stage with a bifocal lens. It allows two images to form within the same eye at the same time. This is the first recorded use of bifocal technology in the animal kingdom.

This ability allows them to switch their vision from up close to long distance helping them find prey.

Once they metamorphose in to their adult form these eyes are reabsorbed and replaced with a compound eye.

Females tend to be slightly larger than males. They measure 1-1.5cm (0.4-0.6in) long.


These beetles are carnivores. They hunt for invertebrates, small fish and tadpoles.

Sunburst diving beetles play an important role in controlling populations of mosquitos by eating the larvae from in the water.

Sunburst Diving Beetle


Sunburst diving beetles are found in the United States and Mexico within North America. In the United States they can be found through the following states - California, Arizona, New Mexico and Texas.


Much of the range of the sunburst diving beetle is located within the Sonoran desert. Some may also be found in montane pine or pine-oak forests. They spend their time in quiet pools of waters.

These pools of water are filled by the flash floods which commonly occur in the desert and fill dry creek beds and gulches.

They have been seen to make their home in man-made habitats such as birth baths and swimming pools.

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Males will work to grasp the female who tends to swim away from him erratically.

Females deposit their eggs in to a slit cut in to the stem of an aquatic plant. Up to 20 eggs are deposited in each clutch. These hatch after 6 days.

The eggs hatch a larva which will develop in the water until it is ready to complete its pupation. These larva have a soft, elongated body. This takes place on the land and they emerge as a fully grown adult.

When food is plentiful they may complete their full lifespan in as few as 28 days.

The larva complete their pupation on dry land.


Sunburst diving beetles are able to perform their namesake dives due to an air bubble which sits under the wings. This allows them to remain underwater for a longer period before having to surface.

These insects will form small colonies.

Along with diving well these beetles are also strong fliers. In the event that their watercourse dries up they will take to the skies and fly to a new pond.

While these animals can be active at any time they appear to be primarily nocturnal.

Sunburst Diving Beetle

Predators and Threats

Natural predators of the sunburst diving beetle include fish, frogs, reptiles, birds and predatory insects.

To defend themselves against predators they can eject a chemical with a foul smell from a gland which is located on top of the head.

Humans affect them through groundwater extraction, pollution, introduction of species and climate change.

Quick facts

Larvae of the sunburst diving beetle may be referred to as "water tigers."

These beetles are also referred to as the yellow-spotted diving beetle.

Sunburst Diving Beetle

Photo Credits

Top, Middle One and Middle Two

Ltshears, CC BY-SA 3.0 <>, via Wikimedia Commons


Fredlyfish4, CC BY-SA 4.0 <>, via Wikimedia Commons


Los Angeles Zoo and Botanical Gardens (LA Zoo). 2021. Sunburst Diving Beetle | Los Angeles Zoo and Botanical Gardens (LA Zoo). [online] Available at: <> [Accessed 22 June 2021].

The Deep. 2021. Sunburst diving beetle | The Deep. [online] Available at: <> [Accessed 22 June 2021]. 2021. Sunburst Diving Beetle | Saint Louis Zoo. [online] Available at: <> [Accessed 22 June 2021]. 2021. [online] Available at: <> [Accessed 22 June 2021].

Sunburst Diving Beetle (Thermonectus marmoratus) Fact Sheet. c2021. San Diego (CA): San Diego Zoo Wildlife Alliance; [accessed 22 June 2021].

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