Fearless Giant Water Bugs Eat Turtles, Ducklings, And Even Snakes

A new study finds that giant water bugs are voracious predators that take down everything from ducklings to venomous snakes after decades of research on the aquatic insects.

Charles Swart, a senior lecturer at Trinity College in Connecticut who has studied the giant water bugs. states that , “They’re lie-and-wait predators. They just take up a position holding onto a plant in the water, and anything that moves in front of them, they’ll grab it and try to eat it.”

The research was published in the March edition of the journal Entomological Science and does an in-depth analysis of the ecology of giant water bugs, which are found almost all over the world and comprise some 150 known species. The largest of them is the Lethocerus grandis and Lethocerus maximus that live in South America and can reach more than four inches.

Study author Shin-ya Ohba, an associate entomology professor at Japan’s Nagasaki University, says he’s been fascinated by the insects ever since he first saw one in a pet store as a seven years old.

Kirkaldyia deyrolli preys on a turtle—a rare observation. PHOTOGRAPH BY SHIN-YA OHBA

He says, “Japanese entomologists like giant water bugs because they have cool morphology. Their front legs, for instance, remind him of Popeye the Sailor when he’s flexing his arms”.

Everything On The Menu

For his research, Ohba studied all existing studies on water bugs, especially the four species native to Japan whom he had researched including the well-studied Kirkaldyia deyrolli. These four are top predators in rice fields and wetlands.

The main consistent theme that emerged was that these insects seem almost fearless in their predation. For example, Ohba reported the first observation of a giant water bug preying on a turtle in 2011.

In spite of their size, the brownish bugs blend in with the plants upon which they perch, dangling upside down so they can breathe via a “snorkel” protruding from their behinds. Once a prey comes within reach, the predators quickly snap their front legs to constrict and grasp the creature with their other legs. The insects then pierce their prey with a dagger-like proboscis, injecting enzymes and maybe anesthetic chemicals.

A giant water bug, Lethocerus deyrollei, attacks a fish in Saitama, Japan. PHOTOGRAPH BY YASUDA MAMORU, MINDEN PICTURES

Swart, who wasn’t involved in this study, notes that it’s uncertain exactly what is inside the water bug toxins and whether they’re truly venomous.

Ample throughout North America, the great spangled fritillary has a beautiful checkered pattern that serves as camouflage in dappled sunlight. Its scientific name is Speyeria cybele, denoting “earth mother.” There are more than 200 species of June beetles commonly called June bugs who emerge in early summer and are often seen flying around lights in the evenings.

He says, “They break down the tissue and then they suck it back up,” adding that in case of larger prey, this can take a few hours of which at least part of the time the victim may remain alive.

Swart adds that the new research is a “really comprehensive review of all that’s known about them.”

Infanticidal mothers

Giant water bugs are unusual among insects as here males take on the bulk of responsibility in caring for the eggs. In some giant water bug species, males guard eggs, up to five at a time, by protecting them from predators like ants. In some others, females glue their eggs directly onto the back of the males who tote them around until they hatch into nymphs.

Ohba’s study notes that in some species like K. deyrolli, females are so keen to find a mate that they even eat other females’ eggs.

Ohba writes, “By destroying the eggs of her competitor, a female can obtain the mating partner of the competitor and make certain that the male takes care of her eggs”.

Moreover, water bug nymphs, whose life stage is 60 days, need to be as tough as adults. In most species, they hatch in a season when smaller prey is not plentiful, forcing them to try for seemingly impossible prey like tadpoles or small fish.

According to Ohba, these nymphs are armed with highly curved front legs, which helps them clasp prey better. Yet in the food chain, what goes around comes around. Swart adds that giant water bugs frequently fall prey to larger fish, ducks, and perhaps raccoons or turtles. In Southeast Asia, even some people eat them fried or boiled.

Why Do We Need Giant Bugs

Although these water bugs sound scary, their position as top-shelf predators implies that they are key to maintaining a healthy ecosystem. Water pollution can potentially harm their populations, and alien species like crayfish and bullfrogs can prey on water bugs. So scientists need to work to ensure clean, invasive-free fresh water for these crucial species.

Ohba says, “We can conserve whole ecosystems through the conservation of giant water bugs.”

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