Thermonectus marmoratus

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Sunburst Diving Beetle
Diving beetle1.svg
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Coleoptera
Suborder: Adephaga
Family: Dytiscidae
Genus: Thermonectus
Species: T. marmoratus
Binomial name
Thermonectus marmoratus
Gray, 1832

Thermonectus marmoratus is a species of diving beetle known by the common names sunburst diving beetle and spotted diving beetle.[1] The beetle has recently become notable when it was discovered that its aquatic larval stage has been found to have used in its principal eyes two retinas and two distinct focal planes that are substantially separated, in the manner of bifocals to switch their vision from up-close to distance, for easy and efficient capture of their prey, mostly mosquito larvae. This is the first ever recorded use of bifocal technology in the animal world.[2]


An enclosure for Sunburst Diving Beetles.

The adult beetle reaches a maximum length of about one centimeter, or half an inch, with females slightly larger than males. The sunburst diving beetle has a black and streamlined carapace covered with bright yellow or golden spots. The male has a suction disk on each foreleg.[3][4]

Behavior and distribution[edit]

Sunburst diving beetles live in ponds and lakes and swim well.[1][3] When their water source dries up they will fly to a new one.

Sunburst diving beetles are found in extreme Southern California, Arizona, New Mexico, Texas, and Mexico, requiring at least a temporary water source. Seen in Moab, Utah.


In the wild, these beetles are useful because they eat other invertebrates including mosquito larvae and pupae. Spotted diving beetles have also been observed swarming a prey item and feeding en masse. In captivity, these beetles will feed on flake fish food and live crickets.[5][6]


  1. ^ a b MORGAN, R.C. (1998). "5". "Windows on the Water World," Backyard BUGwatching. pp. 4–6. 
  2. ^ Dawn Fuller (duly edited) (24 August 2010). "Bug With Bifocals Baffles Biologists". ScienceDaily. ScienceDaily LLC. Retrieved 25 August 2010. 
  3. ^ a b EVANS, D.L.; SCHMIDT, J.O.; EDs. (1990). Insect Defenses, Adaptive Mechanisms and Strategies of Prey and Predators. State Univ. of New York Press, Albany. pp. 482 pp. 
  4. ^ MILNE, L; MILNE, M. (1980). "Marbled Diving Beetle (Thermonectus marmoratus)," The Dobbin Society Field Guide to North American Insects and Spiders. Alfred A. Knopf, NY. pp. 542+ plate 96. 
  5. ^ Arnett Jr, R.H.; Jacques Jr, R.L. (1981). "Thermonectus marmoratus," Simon and Schuster's Guide to Insects. New York, Toronto and London: Simon and Schuster Inc. pp. 86–87. 
  6. ^ MORGAN, R.C. (1992B). "Natural History, Captive Management and Display of the Sunburst Diving Beetle Thermonectus marmoratus," AAZPA/CAZPA Annual Conference Proceedings. pp. 457–464.