Giant Water Bugs: Close Encounters with Toe Biters

It was during one of those long summer vacations that I first came across giant water bugs, not in a scientific sense, but through a direct, rather painful encounter. I was visiting my aunt in Thiruvananthapuram, in the southern Western Ghats, in the mid-2000s. Back then, the riverside lifestyle was intact. People along rivers washed clothes, bathed, and even did dishes in the river. For us kids, this meant a guaranteed visit to the river at least twice a day.

My aunt would often warn me about “toe biters”, but I didn’t heed her warning — why fear something that seemed non-existent? To my young mind, aquatic insects were harmless creatures floating on the surface or diving in, serving no real threat. With shallow waters, abundant pebbles, and crystal-clear currents, the river near my aunt’s house was a haven for endless play. While my aunt was washing clothes, I’d spend hours building pebble stacks, trying to float, and simply enjoying the water.

Bites and Breakthroughs

One day, as I waded through aquatic grasses, I felt a sudden, sharp pain in my toe. Before I could even comprehend what had happened, I screamed, startling everyone around. People rushed over, concerned until they realised what had caused it, “It’s just a toe biter!” someone laughed. Everyone went back to their chores, leaving me in shame and excruciating pain, perhaps just a notch below a hornet sting. It felt like my toe was being crushed under something heavy, the ache lingering long after the bite. Only then did I truly understand why these insects were feared and respected by those who knew their waters.

Little did I know that these seemingly malevolent creatures would later become subjects of my admiration and research. Years later, while working on edible insects in the remote villages of Nagaland, I stumbled upon toe biters once again in a completely different light. While exploring paddy fields, my field assistant suddenly grew excited upon spotting a large water bug. For locals, “toe biters” aren’t nuisances but a prized delicacy. In the waterlogged paddy fields of Nagaland, where cultivation involves seasonal flooding and controlled water channels, toe biters thrive, feeding on small fish and other aquatic organisms.

Accolades and distribution

Toe biters, or giant water bugs, have quite a few accolades to their name. They are the largest insects of the order Hemiptera, with some species growing up to 12 cm long. They are the largest aquatic insects and one of the largest predatory insects in the world. These bugs are ecological indicators of water quality. In several cultures within Southeast Asia, they are a culinary delicacy. They are easily recognisable by their flattened, oval-shaped, dark brown to olive-green bodies, raptorial front legs designed to grasp prey, and a prominent breathing tube extending from their rear, which they use to access air while submerged. Widespread across India, it can be found in a variety of freshwater ecosystems — rivers, lakes, ponds, paddy fields, and small puddles — in the Western Ghats, Northeast India, and the Gangetic plains.

The giant water bug family is Belostomatidae, which includes around 170 species worldwide, spread across nine genera. These insects are distributed across diverse freshwater habitats in North and South America, Asia, Africa, and Australia. About ten species from the genera Lethocerus, Belostoma, and Diplonychus have been documented in India.  

Unique adaptations

Many aspects of giant water bug biology are adapted to aquatic life. They employ a unique breathing mechanism involving snorkel-like tubes at the rear of their abdomen. These tubes extend to the water’s surface, enabling the bug to access atmospheric air while remaining submerged. When the bug surfaces, it takes in air, which becomes trapped in a bubble beneath its wings. This trapped air is then drawn into the body through small openings located along the abdomen (spiracles), thus facilitating gas exchange. Their forelegs have hook-shaped claws for grasping prey, while their flattened hind legs function as oars and propel them through the water. Giant water bugs can latch onto surface plants using their hind legs and swiftly snatch passing prey with their powerful front legs. Upon capturing prey, they pierce it with the sharp rostrum (specialised, elongated and needle-like mouthpart). They inject the prey with a potent toxin that paralyses it and liquefies its internal tissues for easier consumption. The giant water bug’s prey catalogue includes aquatic insects, crustaceans, tadpoles, salamanders, fish, and amphibians. Interestingly, toe biters can capture prey up to 50 times their size.

The life cycle of toe biters involves simple metamorphosis, transitioning from egg to nymph to adult in 1-2 months. Adults typically live for around one year, during which they reproduce and continue the cycle. Parental care is notably unique, particularly in the genera Lethocerus and Belostoma. After females lay their eggs above water on plants or directly on the backs of males (in some species), the males take on the responsibility of protecting and nurturing the eggs until they hatch. They periodically expose the eggs to air to prevent fungal growth and engage in “brood pumping”, i.e., moving water over the eggs to enhance oxygen diffusion. This form of parental care is relatively rare among insects and ensures a higher egg survival rate.

Ethnic delicacy

By June, paddy transplantation is completed in Nagaland’s villages, and by August, villagers return to the terrace fields to weed and capture various aquatic insects, including toe biters. These insects are more prevalent in the warmer parts of the region. In Khonoma village, for example, the upper sections of the terrace fields harbour fewer insects than the lower areas according to Thejavikho Chase of the village. Although there isn’t much meat on them, and they are primarily just exoskeletons, the real attraction is in the fragrant liquid they contain. I’ve observed this delicacy being appreciated in other countries, such as Vietnam, where the liquid is served in droppers alongside soupy noodles. In Nagaland, they are often cooked with bamboo shoot water and combined with other aquatic insects, especially dragonfly nymphs, creating a unique culinary experience. This traditional practice emphasises the integral role these insects play in the diet and culture of the Naga people.

Debunking myths

One common myth about toe biters is that their bite can paralyse a human or even lead to death. This misconception likely arises from the shock and fear caused by the unexpected pain of the bite. While the bite is intended to deter predators, it does not cause serious harm to humans. It’s important to note that toe biters do not actively seek out humans, and bites usually occur when they are accidentally stepped on or handled roughly. Toe biters are more than just creatures of folklore and fear. They play a critical role in regulating the population of other aquatic insects and small vertebrates, making them important components of freshwater food webs. Their presence indicates a healthy aquatic ecosystem, as they require relatively clean, well-oxygenated water to thrive.