Great diving beetle

The great diving beetle is a species in the suborder of beetles known as Adephaga. This aquatic, or water-living, beetle is typically found in ponds, lakes, and marshes. It is given the name great diving beetle, or simply diving beetle, for its excellent swimming abilities.

Kingdom: Animalia

Phylum: Arthropoda

Class: Insecta

Order: Coleoptera

Family: Dytiscidae

Genus: Dytiscus

Species: Marginalis

The great diving beetle is typically about 1 to 1 1/2 inches (2 to 3 centimeters) long. It is one of the largest species of freshwater-living beetles. Like other insects, its almond-shaped body is divided into three parts—head, thorax, or mid-body section, and abdomen, or lower-body section. On its head, the diving beetle has a pair of antennae extending outward on both sides and a pair of compound eyes close together near the front of the insect's head. Compound eyes have multiple lenses that give animals better vision than single lenses. Below its eyes are the biting mouthparts of the great diving beetle.

These mouthparts are divided into the mandibles, the maxillae, and the lips. The mandibles, or jaws, do the main cutting and chewing, while the other parts move the food toward the mouth and digestive system.

Behind the head of the great diving beetle is its thorax, which holds the beetle's six legs. The back legs have thick hairs called swimming hairs. Its thorax is just a small part connecting the insect's head to its elytra, or the hard covers over its rear wings. The two pairs of wings on the great diving beetle are over its abdomen. The head, thorax, and elytra are typically olive-brown, black, or dark brown with a yellow line around the outer edge. Sometimes this insect only appears green when underwater.

The elytra of the great diving beetle are the hardened front wings. The great diving beetle protects its delicate rear wings with its elytra. The females have ribbed elytra, but the males' elytra are smooth. Each covering, or elytrum, is formed from one of the beetle's front wings. When the beetle is resting or swimming, the elytra are smooth, shiny, and flat, but when the great diving beetle takes flight, the elytra lift and the beetle takes to the air by the motion of the rear wings.

The great diving beetle is an aquatic, or water-living, species within the suborder Adephaga. Typically, it is found in small, calm, shallow ponds, lakes, and marshes. It lives under the water but must come to the surface to breathe. It also stores an air bubble under its wings to breathe and stay beneath the surface longer.

At night, the great diving beetle flies from pond to pond in search of food. Its diet includes small fish, other water insects, worms, tadpoles, and snails. The great diving beetle is sometimes called the cleaner of the pond because it also feeds on decaying fish. Fish, birds, lizards, spiders, frogs, and humans prey on these beetles. In some countries, they are a source of food.

In the spring, when the great diving beetle awakes from its hibernation, or winter sleep, it moves out of the leaves and grasses at the bottom of the pond and begins to search for a mate. Once a pair is formed, the male great diving beetle passes a spermatophore, or package of sperm, to the female to fertilize her eggs. Soon after fertilization, the female lays her long, white, banana-shaped eggs individually in the leaves and stems of aquatic plants.

Soon, the eggs hatch into light-brown, segmented larvae. They cannot breathe underwater but have a snorkel called a siphon that sticks out of the water so they can breathe. These larvae are fierce predators. They inject their prey with digestive liquids and suck the liquid using their sharp mouthparts. Eventually, these larval diving beetles dig pupating chambers, or chambers in which they enter their final developmental stage. In these chambers, larval diving beetles molt, or shed, their skins and develop into pupal diving beetles. During its pupal stage, the pupa matures into its adult form beneath the skin of its pupal form. Eventually, it molts its pupal skin and emerges as an adult great diving beetle.

The average lifespan for the great diving beetle in captivity is around 1 to 2 years.

Bibliography

"Diving Beetle." Field Guide to Common Texas Insects, texasinsects.tamu.edu/diving-beetle. Accessed 15 May 2024.

"Diving Beetle Life Cycle." The Australian Museum, australian.museum/learn/teachers/learning/diving-beetle-life-cycle. Accessed 15 May 2024.

"Great Diving Beetle." The Wildlife Trusts, www.wildlifetrusts.org/wildlife-explorer/invertebrates/beetles/great-diving-beetle. Accessed 15 May 2024.