|Lethocerus americanus in Montana, USA|
|Subfamilies and genera|
Belostomatidae is a family of freshwater hemipteran insects known as giant water bugs or colloquially as toe-biters, Indian toe-biters, electric-light bugs, alligator ticks, or alligator fleas (in Florida). They are the largest insects in the order Hemiptera. There are about 170 species found in freshwater habitats worldwide, with more than 110 in the Neotropics, more than 20 in Africa, almost as many in the Nearctic, and far fewer elsewhere. These predators are typically encountered in freshwater ponds, marshes and slow-flowing streams. Most species are at least 2 cm (0.8 in) long, although smaller species, down to 0.9 cm (0.35 in), also exist. The largest are members of the genus Lethocerus, which can exceed 12 cm (4.5 in) and nearly reach the length of some of the largest beetles in the world. Giant water bugs are a popular food in parts of Asia.
Belostomatids have a flattened, obovoid to ovoid-elongate body, and usually the legs are flattened. The hind tarsi have two apical claws and tucked behind the eyes is a short antennae. A short breathing tube can be retracted into its abdomen. Adults cannot breathe under water, so must periodically place the breathing tube at the surface for air (similar to a snorkel).
Their frontal legs are modified into raptorial appendages that they use to grab their prey, except in the African Limnogeton, which has "normal" frontal legs and is a specialized snail-eater. Once caught, the prey are stabbed with their proboscis and a powerful saliva is injected, allowing the Belostomatid to suck out the liquefied remains. Wing pads can be seen from the dorsal view. While the members of the subfamily Lethocerinae can disperse by flying, other species, including Abedus herberti, have a greatly reduced flight apparatus and are flightless.
Belostomatids are aggressive predators that stalk, capture, and feed on fish, amphibians, as well as aquatic invertebrates such as snails and crustaceans. The largest species have also been found to capture and feed on baby turtles and water snakes. They often lie motionless at the bottom of a body of water, attached to various objects, where they wait for prey to come near. They then strike, injecting a venomous digestive saliva with their rostrum. Although their bite is excruciatingly painful, it is of no medical significance. Occasionally, when encountered by a larger animal, such as a human, they have been known to "play dead" and most species can emit a fluid from their anus. Due to this, they are assumed dead by humans only to later "come alive" with painful results.
Belostomatids show paternal care and these aspects have been studied extensively, among others involving the North American Belostoma flumineum and the East Asian Lethocerus (Kirkaldyia) deyrollei. In species of the subfamily Belostomatinae, the eggs are typically laid on the male's wings and carried until they hatch. The male cannot mate during this period. The males invest considerable time and energy in reproduction and females take the role of actively finding males to mate. This role reversal matches the predictions of R. L. Trivers' parental investment theory. In the subfamily Lethocerinae, the eggs are laid on emergent vegetation and guarded by the male.
In some areas, belostomatids are considered a delicacy, and can be found for sale in markets. This is mainly in South and Southeast Asia involving the species Lethocerus indicus. In South and Southeast Asia they are often collected for this purpose using large floating traps on ponds, set with black lights to attract the bugs. Adults fly at night, like many aquatic insects, and are attracted to lights during the breeding season.