Dytiscidae

The Dytiscidae (Greek "dytikos" ("able to dive") is a family of water beetles. They are called predaceous diving beetles. They are about 25 mm (one inch). The largest beetle, "Dytiscus latissimus", can reach 45 mm long.
Most Dytiscidaes are dark brown, black-ish or dark olive in color with golden highlights in some subfamilies. The larvae are called "water tigers". The water tigers will eat tadpoles and glassworms. They will also eat anything small living in the water. There are about 4,000 species in over 160 genera of Dytiscidae.
Food.
The "Cybister" can be eaten by humans. In Mexico, "C. explanatus" are roasted and salted onto tacos. In Japan, "C. japonicus" is used as food. In Guangdong Province, China, several species are eaten. The great diving beetle ("Dytiscus marginalis") are bred for human food. Dytiscidae have been eaten in Taiwan, Thailand, and New Guinea. Birds and other small mammals eat "Dytiscidaes".