Bifocal-vision
Guides
Thermonectus marmoratus
sunburst diving beetle, yellow-spotted diving beetle, spotted diving beetle
Thermonectus marmoratus is a small, brightly colored diving beetle native to southwestern North America and Mexico. Adults are distinguished by black elytra with yellow or golden spots and possess specialized adaptations for aquatic life, including air bubble storage beneath the wings for extended underwater respiration. The species is notable for its aposematic coloration warning of chemical defenses, and for the extraordinary visual system of its larvae—featuring bifocal lenses with dual retinas that constitute the first recorded instance of bifocal vision in the animal kingdom. Larvae are active predators with complex stemmata capable of near and far vision, polarization sensitivity, and behavioral scanning mechanisms to extend their narrow visual fields.