Austroplatypus incompertus facts for kids

The Austroplatypus incompertus is a special type of ambrosia beetle. It is part of the true weevil family and lives in Australia. You can find these beetles in New South Wales and Victoria.

These beetles live in groups, called colonies, inside Eucalyptus trees. They are the first beetle known to be "eusocial." This means they live in a highly organized society, much like ants or bees. In an Austroplatypus incompertus colony, there is one female who lays all the eggs. A few other females protect her and do most of the work. These beetles are also amazing because they seem to be the oldest "farmers" on Earth! They started growing fungi for food almost 90 million years ago.

Meet the Austroplatypus Beetle

This section describes what the Austroplatypus incompertus beetle looks like and how it grows.

How They Grow

A baby A. incompertus egg is tiny, about 0.7 millimeters long. It goes through five growth stages, called instars. In each stage, its head gets a bit bigger. After these stages, it turns into a pupa, like a butterfly in a cocoon. Then, it becomes an adult beetle. An adult beetle is about 6 millimeters long and 2 millimeters wide.

Adult Beetles

Adult Austroplatypus incompertus beetles have a long, tube-shaped body. Male and female beetles look different. This is called sexual dimorphism. Surprisingly, the males are much smaller than the females. This is unusual for this type of beetle. Female beetles have special wing covers, called elytra, that help them clean their tunnels and defend their home. Only females also have special pouches, called mycangia, to carry their food.

Where They Live and What They Eat

Like other ambrosia beetles, A. incompertus lives in a special partnership, called symbiosis, with ambrosia fungi. They dig tunnels inside living trees. In these tunnels, they grow their fungal gardens. This fungus is the only food they eat.

Starting a New Home

When a female beetle is ready to start a new colony, she carries tiny fungal spores in her mycangia. She digs into a new tree, usually in the autumn. It takes her about seven months to dig deep enough, about 50 to 80 millimeters, to lay her eggs.

Their Favorite Trees

Scientists from the United States Department of Agriculture (USDA) studied many types of wood from Australia. They found A. incompertus in most of them. These beetles like to live in many kinds of Eucalyptus trees, such as Eucalyptus baxteri, E. botryoides, and Corymbia gummifera. Unlike most ambrosia beetles, A. incompertus chooses to live in healthy, strong trees, not damaged ones.

Where They Are Found

A. incompertus beetles only live in Australia. They have been found in different parts of New South Wales. Their home range stretches from Omeo in Victoria up to Dorrigo in northern New South Wales. It also goes west to the Styx River State Forest.

How They Live Together

Their Social Life

When a female beetle starts a new colony, she burrows deep into a living tree. She then branches off to lay her eggs and plant her fungal spores. When the young beetles grow up, the males usually leave. About five females stay behind. These females soon lose the last four parts of their back legs. After this, the tree closes up the only entrance to the colony. This means the remaining females cannot leave or find a mate. They become "worker" females. They help maintain the tunnels, dig new ones, and defend their home. This helps keep the colony organized.

What Eusociality Means

A. incompertus is one of the few animals, besides ants, bees, and termites, that is eusocial. Eusocial insects live in large groups with many generations. They work together to raise their young. Often, some individuals give up their own chance to have babies to help the group. These "sterile" workers do all the non-reproductive jobs. This "altruism" (helping others without personal gain) works because helping close relatives means their shared genes are passed on.

For an animal to be called eusocial, it must meet three rules:

• Different Jobs: The group must have different jobs for different members. In A. incompertus, one female lays eggs, while others dig and protect.
• Overlapping Generations: Adults and their offspring must live together at the same time. This happens in A. incompertus colonies.
• Cooperative Care: All members must help care for the young. A. incompertus beetles do this too.

Why They Became Eusocial

Scientists are still trying to understand why these weevils became eusocial. One idea is called "fortress defense." This means they work together to protect a valuable home and food source. A. incompertus beetles dig tunnels in trees with only one entrance. This fits the "fortress defense" idea. The female beetle brings the food (the fungus) into the tunnels she digs. Also, female beetles have strong spines on their wing covers, which might help them defend the tunnels.

Another idea is "life insurers." This means helping relatives increases the chances of their shared genes being passed on. It's possible that helper females stay in the colony hoping to take over if the main female dies. Living in a live tree might offer a bigger and more stable home, but it needs constant work to keep the tunnels safe. Scientists are still studying these beetles to learn more about how such unique social behavior evolved.