Meet The Giant Water Bugs That Eat Ducklings (But Are Good Dads!)

Giant water bug (Lethocerus deyrollei) in Japan. It cannot fly unless its muscles are very hot. feathercollector/Shutterstock

Humans are often unfairly squeamish when it comes to insects. Most of them are harmless, after all. Some are even useful to us. Giant water bugs are in the latter category, but many people would rather think of them as nightmare-inducing, given that they can feed not just on insects and invertebrates but also on fish, snakes, turtles, and even the occasional duckling.

You might not agree with their dinner choices, but this family of insects is absolutely fascinating. In an extensive review of decades' worth of studies on giant water bugs, researcher Shin-ya Ohba, an associate entomology professor at Japan's Nagasaki University, discusses the many intriguing facets of these bugs. The work is published in Entomological Science.

There are around 170 species found worldwide in freshwater ponds of the Americas, Africa, and Asia. They can go from 0.9 centimeters (0.35 inches) to a whopping 12 centimeters (4.5 inches). Not only are they natural enemies of certain dangerous insects such as disease-carrying mosquitos but they also eat pests in fisheries and are considered a popular food in some parts of Asia.

North American Giant Water Bug (Belostoma flumineum) eating a fish. AndrewASkolnick/Shutterstock

One of the most intriguing facts is the role of the male in caring for the young. Depending on which subfamily they belong to, the male insects might either carry the eggs on their back or guard the eggs laid on vegetation. Until they hatch, the males don’t mate. In fact, it's the females that have to fight to find a mate. Some females will happily destroy the brood of another one, just to have a chance with the male. The male would attack her, but given the larger physical size of the female, he might not be able to overcome her.

As long as the air temperature is high enough, the insects can migrate by flying. Researchers have shown that certain species have flight capabilities all year round but only fly if their muscle temperature reaches approximately 40°C (104°F).

In all but one genus, the front legs are modified into raptorial appendages. The insects use them to take hold of their prey before injecting them with their saliva, which slowly melts their interior. Their bite is not dangerous to humans, they don’t carry any disease, and they can’t cause a major injury, but their bite is painful and has earned them the nickname "toe-biters".

Like many other species, giant water bugs are at risk from pollution and invasive species. Ohba notes we must protect these critters to maintain a healthy ecosystem. 

[H/T: National Geographic]

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