Hunting the Depths with the Diving Beetle
- HYUN SIM
- Feb 20
- 3 min read
The Great Diving Beetle (Dytiscidae) is a predacious beetle that hunts underwater as the name suggests. The colors of this oval-shaped beetle can range from black to brown to olive, and some even have yellow marks (MDC). It is streamlined but narrow near the end of the head. Upon its head sits its threadlike antennae (MDC). On the opposite side of the body are the hindlegs which are flat and fringed with hair, well-equipped for swimming (MDC). Most adults grow to 1cm-2cm in length. Specimens of the Brazilian and European variations are much larger though, growing up to 4.75 cm. The Australian variation, on the other hand, is the smallest at around 0.9mm (Wikipedia).
What sets the Great Diving Beetle apart is that it uses its hindlegs to dart through the water. It kicks and pushes the water with both legs simultaneously, this trait sets it apart from the water scavenger beetle (MDC) and it allows the Great Diving Beetle to hunt its prey. It doesn't back down from to larger prey, going after small fish, tadpoles, and frogs. Despite hunting underwater prey, it cannot breathe underwater. It actually stores air under its elytra (Wildlife Trusts). Sometimes adults can be seen poking the back end of their abdomens above the water to replenish the air supply (Wildlife Trusts). It is the most diverse beetle in aquatic environments. It can be found in any body of fresh water including birdbaths and swimming pools (Wikipedia). They end up in such locations by being strong fliers and migrating when their current home dries up.
The Great Diving Beetle lays its eggs on underwater vegetation. The males sport pads on their forelegs that attach to the deeply grooved wing case of females during mating (Wildlife Trusts). The eggs hatch into larvae that are considered one of the most feared predators in the insect world. These larvae are called Water Tigers.
Water Tigers are also called the Underwater Devil's Coach Horse in reference to another predator on land with the same name and similar features (Wikipedia). They hunt by attaching themselves to an underwater brush with their back legs and waiting completely still. When prey swims by, usually a glass worm or tadpole, they lash out and restrict the prey with their front legs (Wikipedia). The final blow is inflicted when the Water Tiger brings down its large fangs on the struggling prey. A gruesome fact about the Water Tiger is that it will often discard a half-eaten carcass if another live meal comes into range (Wikipedia). Water Tigers will bury themselves in the mud and go under a pupa state. After a week, the adult Great Diving Beetle emerges (Wikipedia).
A folk Cherokee creation story involves a Great Diving Beetle bringing up mud from the planet's swirling depths to create lands on Earth (Wikipedia). Although it is a creator deity in one creation narrative, the Great Diving Beetle is also a food item consumed in different parts of the world. It is described as having a bland taste while also not having that much meat. This beetle is consumed in Japan, China, Mexico, New Guinea, Taiwan, and Thailand (Wikipedia).
People aren't the only ones that eat these beetles. They have many predators: birds, reptiles, mammals, and other vertebrae (MDC). Among them, the most common predators are fish, which is also one of the reasons why the number of these beetles is declining rapidly. The other reason is habitat loss despite being relatively resistant to urbanization. Climate change has dried up many freshwater bodies and people pollute many others.
The Great Diving Beetle is another beetle affected by climate change and human actions. Being one of the few aquatic insects, the Great Diving Beetle is a specimen that scientists and even engineers cannot afford to lose. Awareness and care need to be promoted for these beetles to continue on.
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