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Thermonectus marmoratus is a species of diving beetle known by the common names sunburst diving beetle and spotted diving beetle. 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.
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.
Behavior and distribution 
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.
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- Dawn Fuller (duly edited) (24 August 2010). "Bug With Bifocals Baffles Biologists". ScienceDaily. ScienceDaily LLC. Retrieved 25 August 2010.
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- 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.
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- 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.