Giant Water Bug

The giant water bug is an aquatic insect that belongs to the Heteroptera family - Belostomatidae. They are large predatory aquatic insects that have the largest body size in the entire Heteroptera family. All over the world, there are around 170 species, which are found in freshwater habitats. More than 110 species are found in the neotropical realm with more than 20 in Africa. They are generally encountered in freshwater ponds, marshes and slow-flowing streams, suspending below the surface and respiration through two abdominal appendages which act as their siphons. Mostly, the species are 0.8 inches long with the smallest as 0.35 inches and the biggest as 4 inches.

During the mating season, they fly from one pond to another pond or pool of water. During this flight, they fly to light in large numbers because of which they got the name “electric light bugs”. The giant water bug bite with the help of their strong beak and they can also pinch with their front legs. The giant bug prey on aquatic insects, small fish, frogs, tadpoles, small birds, and other organisms that they are able to capture. They inject powerful enzymes into the prey to kill them. The adult members of the genus Lethocerus are considered a delicacy in Asia and are eaten as fresh and cooked both.

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Giant Water Bug: Scientific Classification

Giant Bug: Description

The giant water bug belongs to the order Hemiptera - the “true bug”. They are sometimes confused with the roach or the giant water beetle. They have a tan or brown coloured flat, oval-shaped body. If we look at them closely, we will find a short and pointed beak on the underside of their head and their wings that overlap at the bottom end of the abdomen, which, if looked at carefully, will look like “X”. This giant water insect breathes through its behind, carrying its own air supply.

The body of the giant bug is designed in such a way that it makes them an intimidating predator and it is well suited for hunting in its habitat. Their forelegs are tipped with a hook-shaped claw, which helps them in grasping and holding the prey. The big water bug takes the help of its flattened hind legs to swim. With the help of these hind legs only that they catch hold of a plant that is growing close to the surface of a freshwater source. Keeping themselves in that position, they catch the prey that passes by with the help of their most powerful forelegs. 

The giant water bug immediately pierces the prey with its sharp beak and injects the powerful toxin. This harmful toxin has two functions - it first paralyses the prey and then liquefies the internal parts of the prey's body so that the big water bug can suck up a liquid repast.

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Giant Bug: Habitat and Distribution

The giant water bugs are usually seen suspended in the freshwater ponds, marshes, and slow-moving rivers and streams, where the tip of their abdomen pierces the water surface and the brown, oval body hangs below. They are widely distributed over North America but for many species, the exact range is not known. 

Giant Bug: Feeding and Behaviour

The giant water bug feeds on insects, salamanders, tadpoles, snails, and even small fishes. Some of the species are known to kill prey many times their own size. They first grasp the prey with their “raptorial” forelegs and then injects the venomous digestive saliva into the body of their prey. Injection of this venomous saliva helps them to then suck out the liquefied remains. They do not have lungs and hence, take oxygen through tiny holes present in their body wall that connect to the air-filled tubes known as tracheae.

They have an appendage on the tip of the abdomen, which extends above water to collect oxygen. This is the reason why they are sometimes seen tipped at an angle facing downward underwater, with just the rear end at the surface where they are actually breathing. The giant water insect dives underwater, carrying air like a bubble under its wings, which can slowly diffuse into their body while they remain submerged.

Though the giant water bug bite is severely painful, it is of no medical significance. When they are encountered by a larger animal, they act as if they are dead and most of the species emit a fluid from their anus.

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Giant Bug: Reproduction

In late spring or in early summer, the giant bug adults mate and lay a batch of more than 100 eggs. In some genera, such as Belostoma and Abedus, the females forcefully glue their eggs onto the backs of the males to remain there until they are hatched. In other genera, such as Benacus and Lethocerus, the eggs are deposited at the nearest vegetation. The males then take care of the eggs till they are hatched protecting them from the predators as well as bringing them to the surface for oxygen.

The males do not mate till the eggs are hatched. Rather, the females fight to find a suitable mate. In the year 1985, Kraus curiously reported that if the males of sufficient size are not available, the females carry the eggs on their back. In some species, such as K. deyrolli, the female eats another female’s egg to find a mate. By doing so, she makes sure that she gets a partner to mate and take care of her eggs. Some female Lethocerus are also famous for ripping apart the egg clutches deposited by other females when there aren’t enough males.

Mating is a long process for the back brooding species. At first, the male does some pushups in the water. By doing this, they send signals to the females to respond in the form of vibrations. Females then respond to their signals. After this process, when the male and the female find the perfect mating partner, they mate. The female then climbs on the back of the male to lay a few eggs. The male shakes her off and they mate again. The female again climbs on the back of the male to lay a few more eggs before being shaken off. This process continues until around 150 eggs are deposited at the back of the male. This takes a lot of time. 

The life cycle of the big water bug involves simple metamorphosis. The nymphs hatch in about 2 weeks. They (the nymphs) resemble adults and go through five developmental stages where they shed their skin to move from one stage to the next. The life stage of the giant water bugs lasts for around 60 days where their survival becomes as tough as it is for the adults. In most of the species, they hatch in a season when the small prey is scarce and hence are forced to prey on small fish and tadpoles which is a little difficult for them. The nymphs have highly curved front legs to help them to catch the prey easily. 

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Giant Water Bug: Fun Facts

• Giant water bugs bite between the toes of unsuspecting human feet. This is the reason why they are called the toe-biters.  

• The giant aquatic insects can fake their death if they are removed from the water. 

• When the giant bug is disturbed, they squirt unpleasant-smelling fluid from the anus which can be smelt for a few feet. 

• The largest true bug is a giant water bug - Lethocerus maximus, which is around 5 inches long.

• The giant water bugs sometimes become cannibals - they eat their own young ones or the young ones of other females. 

• The giant bugs take several hours to mate, especially the back brooding species.

• As the name suggests, all the “giant water bugs” are actually not “giant”.

• They have good flood avoidance behaviour. Whenever they sense a flood they move away from the stream. They find a shelter, which is far away from the stream and come back only when the flood is cleared to carry out their regular activities. 

• The species  Lethocerus indicus of giant water bugs are eaten in South and Southeast Asia.