Giant Water Bug: The Beast of Pests

a giant water bug on the ground

Giant Water Bug Facts

If you aren’t familiar with the giant water bug, these fascinating creatures are worth getting to know. These bugs are members of the insect order Hemiptera and can grow up to four inches in length. In the United State and Canada, these bugs are often confused with beetles or roaches. However, a giant water bug is flat, tan, and has a short, pointed beak on the underside of its head.

The giant water bug is found all over the world, with habitats in almost every climate. The most aggressive species of water bug to lookout for lives in eastern Asia. However, most species of giant water bugs will not come close to or attack a human unless they feel threatened.

Giant Water Bug on ground
Giant Water Bug

Although the giant water bug species has a claim to fame as the largest true bug in the world, this family of insects is not always giant. In fact, one species of giant water bug from northern South America is less than a centimeter long! While some giant water bugs are quite small and don’t live up to the name, this species definitely makes its mark on aquatic landscapes.

What does a giant water bug eat?

Giant water bugs, which are usually over two inches long, are insect predators. In their immature stages, they look almost exactly like the adults, and nymphs (or immature water bugs) feed in almost exactly the same way as the adults do. They are bold, aggressive hunters, not afraid to hunt prey that is much larger than they are.

Giant water bugs have a wide range of prey, and most of their diet is carnivorous. Giant water bugs will eat aquatic insects in larvae and adult stages, as well as crustaceans, tadpoles, fish, amphibians, and even salamanders. They have been detected hunting snakes, baby turtles, and will occasionally accidentally bite a human toe!

giant water bug on stony ground
The giant water bug is designed to kill and is well-suited for hunting in a variety of habitats. By Ryan Hodnett – Own work, CC BY-SA 4.0, 

Its anatomical design and hunting strategies are quite similar to those employed by other hunters, such as spiders. It has hooked claws to help grasp prey and swims with flattened hind legs that function much like the oars on a boat. It is incredibly powerful as it pierces its victims with its sharp beak.

Once a giant water bug has attacked its prey, it injects it with a toxin to paralyze the prey and liquify the innards of the body so the bug can eat quickly. As a result of this unique adaptation, giant water bugs have the ability to catch and eat animals up to fifty times their size. They have been recorded taking down garter snakes and even turtles.

What are giant water bugs’ predators?

In some cases, humans are even considered giant water bug predators. Although this mostly consists of accidental threats, such as when a human squashes a bug by mistake, in some cultures giant water bugs are considered delicious delicacies. They are a popular food in certain parts of Asia, where chefs fry them in dishes that taste much like watery scrambled eggs.

wattled jacana eating a giant water bug nymph
By Bernard DUPONT from FRANCE – Wattled Jacana (Jacana jacana) with a Giant Water Bug (Belostomatidae) nymph in its bill …, CC BY-SA 2.0, 

Usually, water bugs fall victims to larger hunters such as birds, fish, and other aquatic predators. Giant water bugs have a unique adaptation that helps them avoid detection and consumption. They can lie motionless and their coloring makes them resemble dead, decaying leaves. This camouflage helps them hide from predators, as well as to sneak up on unsuspecting prey. They can also ooze fluid from their anuses to help create the illusion that they are dead. They employ this strategy occasionally while hunting, but most often if they feel threatened.

How does a giant water bug breathe?

Giant water bugs, unlike many other water-dwelling creatures, do not have gills. Therefore, they need to have a unique adaptation to hunt and live underwater.

Insects do not have lungs like vertebrates do. Instead, giant water bugs breathe through pores on their bodies. These pores are called spiracles. Their spiracles are divided into tunnels, known as trachea, which delivers oxygen to all of their body’s other tissues. They do not have lungs that supply oxygen to the blood. They instead are like “portable air supplies” to themselves, breathing underwater from air bubbles that are trapped and then filtered through their spiracles, like an underwater scuba system.

Where are giant water bugs found?

There are few giant water bugs in the world. The life cycle of the giant water bug is short, with adults living only for about one year. Giant water bugs tend to stick in family groups throughout their lives. Female bugs lay their eggs on plants growing out of the water before male bugs guard the eggs. Once the eggs hatch, the babies immediately begin hunting for their own food.

Male giant water bug guarding eggs on its back
Male giant water bug guarding eggs on its back

In many locations, giant water bugs are active throughout much of the year but are most active in late summer and early fall. They usually only make contact with people as the weather begins to cool. During this time, they will fly about, as they are attracted to light. While water bugs won’t deliberately attack humans, they can initiate a painful bite.

Giant water bugs are found throughout the northern United States and Canada, as well South America, Europe, and Asia. The insect enjoys a habitat throughout much of the world’s aquatic habitats. They prefer to live near standing or gently moving bodies of water, such as ponds, marshes, and streams.  They always live in freshwater habitats.

Because water bugs are often confused with other pests such as cockroaches, many people panic when they first spot them on their property. Luckily, they do not carry the same kinds of diseases and, while disgusting, can be easily and painlessly eliminated if you have an active infestation. 

Getting rid of giant water bugs in the home

You can get rid of water bugs on your property in a number of ways. Natural repellents and pesticides include vinegar spray, cooking oil, diatomaceous earth, algaecide, and alcohol. These treatments help to eliminate the food supply of giant water bugs and also help to make the living conditions of the water bug much less desirable.

Giant water bugs will rarely come into the home because they prefer, as their name implies, to be in the water. However, an unclean or damp home can attract giant water bugs.

Make sure you keep your garbage in a separate, clean location, and clean your floors regularly to limit attracting other critters which may be a food source for giant water bugs. You should also keep surfaces such as the laundry room, bathroom, and kitchen dry, as moisture attracts water bugs. Make sure all entry points to your home, such as cracked pipes, window frames, or roof joints, are sealed so that water bugs cannot enter your home. If those tips don’t work, consider calling a professional.

While giant water bugs are not dangerous to your health or safety, unless you are allergic to their bites (which is very rare), they are unsightly pests that don’t belong in your home.

These interesting creatures have been around for millions of years. If you notice a giant water bug, the best strategy is to just leave it alone. It won’t harm you if you don’t harm it, and it can have a positive effect on reducing the population of other undesirable species on your property, such as amphibians and snakes.


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