Have you seen the beautiful Predaceous diving beetle? No, then you must have known it by different names like diving beetle or true water beetle. These are amusing, dynamic beetles that are well adapted to aquatic life. Though more than 4,000 species are in their family, abundant and diverse, their life history is least known! More than 550 species are spread in North America. They belong to the largest beetle family, Dytiscidae, meaning 'able to dive' in Greek.
Have you wondered why they are called predaceous? Because the water beetle adults and larvae can voraciously feed on anything they find within their reach underwater, including larval fish, tadpoles, and glass worms! The amusing part is, they can leave the water and fly, considerable distances, in large numbers. They slowly crawl to the ground, at surface level, to fill their air sacs before flying. When they re-enter the water, they dive back at high speeds.
What type of animal is a Predaceous Diving Beetle?
Predaceous diving beetles are insects, of order Coleoptera and genus Dytiscus. They belong to the family of water beetles. Beetles have a history of existence of more than 225 million years! A famous British biologist, J.B.S Haldane said, "God has an inordinate fondness for beetles."
What class of animal does a Predaceous Diving Beetle belong to?
Diving beetles belong to the class Insecta. These insects are found preserved in the deposits of frozen sediments.
How many Predaceous Diving Beetles are there in the world?
Though the number of diving beetles in the world is unknown, there are 4,000 described species of these aquatic insects under multitudes of genera. The number of species in ground beetles can go up to 40,000! Their total population is 18 times more than the vertebrates.
Where does a Predaceous Diving Beetle live?
You can find diving beetles across the world. In Europe and Brazil, you can see some of the large-sized species. Smaller-sized cousins are found in Australia. Some species of eastern Asia are large and are eaten by humans.
What is a Predaceous Diving Beetle's habitat?
Predaceous diving beetles live in freshwater bodies like ponds, lakes, and streams. They prefer shallow weedy ponds or saltwater ponds and do not prefer fast-moving water bodies. A few species, which are eyeless, are found in deep wells. They also move to the ground, sometimes. The beetle larvae, once mature, move to the surface and to the ground to pupate in moist sand or mud.
Who do Predaceous Diving Beetles live with?
It is not explicitly known if this Dytiscus live in groups. But, in some species of beetles, a queen beetle establishes a colony of beetles with the help of sister beetles. Such queen beetles live for 10-20 years or even up to 30 years in certain cases. Not all queen beetles succeed in building such colonies.
How long does a Predaceous Diving Beetle live?
The Predaceous diving beetles can live for two to three years. The life cycle of these beetles has four stages: egg, larva, pupa, and adult. Many of these species produce one generation every year.
How do they reproduce?
The mating season for Predaceous diving beetles starts in November and extends till March. Males have cups on the first pair of legs, which are streamlined and look like suckers so that they can easily hold on to the female's smooth surface during mating. Then the female releases 30-50 eggs which latch onto the aquatic plants in water or organic debris on soil. Do you know that their larvae are called water tigers? Sounds amusing, right! Rightly named, the water tigers are gruesome predators with a voracious appetite! They are aquatic, with a crescent-shaped body, long tail, and sickle-shaped jaws. Breathing is done via spiracles on the abdomen and stays hanging on the water surface. Larvae can breathe with their long gills or through the skin.
The beetle larvae hatch in about 10-14 days, then they move to the water surface, then to the ground, and pupate in moist chambers of sand or mud. After about a week, they emerge as adults.
What is their conservation status?
The Predaceous diving beetles' conservation status is Least Concern. They are abundant, but their main threat is diminishing water habitats. They prey on several birds, mammals, reptiles, and vertebrate predators despite their chemical arsenal digestive juices. Their most essential predators underwater are fish. Hence their existence automatically reduces in fish-less water bodies. A couple of species are protected in Europe by ensuring such water habitats have enough fish.
Predaceous Diving Beetle Fun Facts
What do Predaceous Diving Beetles look like?
Predacious diving beetles belong to the order Coleoptera and the family Dytiscidae. They have exoskeletons with a shiny and smooth surface with a streamlined convex body. With either brown or black color, some species can have spots or mottling or lines on the wing covers called Elytra. Their antennae are thin and hair-like. Their hind legs are fringed with hairs and have claws, on the end, to aid swimming underwater. When underwater these invertebrates breathe through spiracles, located on the abdomen, under elytra. They fill the spiracles with enough air to breathe while swimming on the ground. They can live underwater for a long time, anywhere between 10 minutes to 36 hours!
How cute are they?
We may find them primarily cute and beautiful but can be a bit creepy to some! Their varied colors like red, black, olive, or with spots make us wonder about nature and its astonishing creations.
How do they communicate?
These aquatic beetles communicate primarily through chemicals like pheromones, kairomones, and allomones. Pygidial glands, prothoracic defensive glands, and pupal glands release these chemicals. The males identify the females by the scent of these secretions. Water tigers are adept at pretending to be dead until their prey comes close to them, and they suddenly attack the prey injecting its digestive chemical.
Some species make sounds by vibrating their mouthparts. Did you know that glowing in the dark is also a form of communication for some species?
How big is a Predaceous Diving Beetle?
Generally, the insects of the family Dytiscidae are about an inch long, though there can be significant variations in sizes. They could be about 50 times larger than a small red ant which is very commonly seen!
How fast can Predaceous Diving Beetles move?
These beetles of order Coleoptera are pretty slow when they are on the ground. They are food for birds and mammals. When they sense their predator, they can be fast enough to dive into the water and become speedy swimmers!
What are the male and female names of the species?
There are 4,000 species of these aquatic insects! The male species are called male beetles, and females are called female beetles.
What would you call a baby Predaceous Diving Beetle?
The larvae of Predaceous diving beetles are called water tigers. Next comes the pupa stage, and then they mature into adults.
What do they eat?
The food of these aquatic insects consists of frogs, small fish, salamanders, and toads. They can prey on animals larger than them. Through their jaws, they pump a digestive juice into the prey, which kills it as well as partially digests it. It then sucks the softened tissues of its prey like tadpoles and small fish.
Are they harmful?
These aquatic beetles, which are invertebrates, are generally harmless, though they are capable of biting. They are helpful because they prey on small harmful insects.
They can be considered damaging in fish hatcheries because their food can consist of small fish. Sometimes they can create a nuisance by flying in places of human habitat and interrupting people's work.
Would they make a good pet?
You can have this bug as a unique pet as they are easy to manage and not harmful. It is essential to have them in a closed aquarium to make sure they don't fly out. Being invertebrates, they need much less food and can maintain self-cleaning ecosystems. You can quickly get rid of it by leaving it in the wild.
Did you know...
Predaceous diving beetles are known to swarm the windshield of a car, they could mistake the glass for an inviting pond!
In East Africa, adolescent girls are known to collect the beetles and have them bite their nipples to induce breast growth. This is a traditional practice for them.
Why have a Predaceous Diving Beetle in your pond?
They can keep the pond clean as they eat small insects. But, the pond cannot have fish as they compete with each other for food and prey on each other.
How do you catch a Predaceous Diving Beetle?
It is easy to catch the diving beetles using a fine-net mesh or bottle traps. As they generally reside at the bottom of the freshwater ponds, it may require some effort to locate them.
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