Giant Water Bugs, Family Belostomatidae

Giant water bug with eggs on its back.
Getty Images/PhotoLibrary/John Cancalosi

There's a reason members of the family Belostomatidae are called giants. The giant water bugs include the biggest insects in their entire order. North American species can reach 2.5 inches long, but the size record for this family belongs to a South American species that measures a full 4 inches in length at maturity. These hulking Hemipterans lurk below the surface of ponds and lakes, where they're known to nip at the toes of unsuspecting waders.

What Giant Water Bugs Look Like

Giant water bugs go by a number of different nicknames. They're called toe biters for their habit of sampling people's feet (which, as you might imagine, is a startling and painful experience). Some call them electric light bugs, because as adults these winged behemoths can and do fly, and will show up around porch lights during mating season. Others call them fish killers. In Florida, people sometimes call them alligator ticks. No matter the nickname, they're big and they bite.

Members of the family of giant water bugs share certain morphological traits. Their bodies are oval and elongated in shape, and appear flattened. They have raptorial front legs, made for grasping prey, with thick femora. Giant water bugs have short heads, and even shorter antennae, which are tucked beneath the eyes. A beak, or rostrum, folds under the head, just as in terrestrial true bugs, like assassin bugs. They breathe by means of two small appendages at the end of the abdomen, which functions like siphons.

How Giant Water Bugs Are Classified

  • Kingdom: Animalia
  • Phylum: Arthropoda
  • Class: Insecta
  • Order: Hemiptera
  • Family: Belostomatidae

What Giant Water Bugs Eat

A giant water bug eats just what you would expect a large, predaceous, aquatic insect to eat: other insects, tadpoles, small fish, and snails. They'll eat whatever they can catch, and they don't concern themselves with finding small prey. Giant water bugs can overpower critters several times their size with their strong, grasping forelegs. According to some sources, giant water bugs have even been known to capture and consume small birds.

Like all true bugs, giant water bugs have piercing, sucking mouthparts. They pierce their prey, inject them with strong digestive enzymes, and then suck up the pre-digested bits.

The Life Cycle of Giant Water Bugs

Giant water bugs undergo incomplete metamorphosis, just as all true bugs do. The young eclose (emerge from their eggs) looking much like miniature versions of their parents. The nymphs are entirely aquatic. They molt and grow several times until they reach adulthood and sexual maturity.

Interesting Behaviors of Giant Water Bugs

Perhaps the most fascinating thing about giant water bugs in the way they care for their offspring. In some genera (Belostoma and Abedus), the female deposits her eggs on her mate's back. The male giant water bug is tasked with caring for the eggs until they hatch in 1-2 weeks. During this time, he protects them from predators, and regularly brings them to the surface for oxygen. He will also move to stir up the water around his body, keeping it oxygenated. In other species (genus Lethocerus), the mated female deposits her eggs on aquatic vegetation, above the waterline. But males still play a role in their care. The male will usually stay submerged near the plant's stem, and will periodically climb out of the water and wet the eggs with water from his body.

Giant water bugs are also known to play dead when threatened, a behavior is known as thanatosis. If you happen to scoop up a giant water bug in a dip net while exploring your local pond, don't be fooled! That dead water bug might just wake up and bite you.

Where Giant Water Bugs Live

Giant water bugs number about 160 species worldwide, but only 19 species inhabit the U.S. and Canada. Throughout their range, giant water bugs live in ponds, lakes, and even drainage ditches.


  • Borror and DeLong's Introduction to the Study of Insects, 7th edition, by Charles A. Triplehorn and Norman F. Johnson.
  • Guide to Aquatic Insects and Crustaceans, Izaak Walton League of America.
  • Belostomatidae, University of California-Riverside. Accessed February 21, 2013.
  • Giant Water Bugs, Electric Light Bugs, Lethocerus, Abedus, Belostoma (Insecta: Hemiptera: Belostomatidae), by Paul M. Choate, University of Florida Extension. Accessed online February 21, 2013.
  • Giant Water Bugs, Electric Light Bugs, University of Florida. Accessed February 21, 2013.
  • Family Belostomatidae - Giant Water Bugs, BugGuide.Net. Accessed February 21, 2013.
  • Giant Water Bug Parents, The Dragonfly Woman. Accessed February 21, 2013.
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Your Citation
Hadley, Debbie. "Giant Water Bugs, Family Belostomatidae." ThoughtCo, Aug. 26, 2020, Hadley, Debbie. (2020, August 26). Giant Water Bugs, Family Belostomatidae. Retrieved from Hadley, Debbie. "Giant Water Bugs, Family Belostomatidae." ThoughtCo. (accessed February 9, 2023).