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Sunburst Diving Beetle (Thermonectus marmoratus)

Look for the Sunburst Diving Beetle, as well as the Green Diving Beetle, and other fascinating creatures in Connecticut’s Beardsley Zoo’s Bug House throughout the warmer months of the year.

The Sunburst Diving Beetle recently become notable when it was discovered that its aquatic larval stage has been found to have two retinas and two distinct focal planes in their principal eyes that are substantially separated. This means they can switch their vision from up-close to distance as if they were wearing bifocals. This enables easy and efficient capture of their prey. This is the first-ever recorded use of bifocal technology in the animal world.

Sunburst Diving Beetles are black with bright yellow spots. The spots warn predators that they can protect themselves by releasing a chemical that tastes bad. Sunburst Diving Beetles are also called Spotted Diving Beetles. They are small beetles. Adults grow to approximately 1/2 of an inch in length. They have a pair of thin antennae and three pairs of legs. Their back legs have a thick fringe of hairs to enable strong swimming. The females are slightly larger than the males. The males also have suction disks on each foreleg.

Sunburst Diving Beetles breathe oxygen but they spend much of their time underwater. Adults are able to do this by creating a bubble of air that they take underwater. While floating on the water the Sunburst Diving Beetle will tip its abdomen up in the air and gather the air under their wing covers to use them like the air tanks human scuba divers use. They can stay submerged for several minutes. Larvae have a siphon like a snorkel coming out of the end of their bodies that they can raise above the water line so they can breath.

Sunburst Diving Beetles are great swimmers but they can also fly. If a pond dries up they can fly to another pond.

Ponds, lakes and slow-moving streams.

They are native to the southwestern United States and Mexico.

Carnivores – they eat other invertebrates that live in or fall into the water. Mosquito larvae make up the majority of their diet but they will occasionally eat tadpoles and small fish. 

Family Life:
The Sunburst Diving Beetle female will lay eggs in the stems of aquatic plants by cutting a slit into the stem. The Sunburst Diving Beetle goes through a complete metamorphosis from egg to larvae to pupa to adult. Their larvae are called “water tigers”.

Life Span:
Little is known regarding the life span of these insects. 

Not listed.