World’s largest insect, Africa’s giant Goliath beetle, faces extinction Premium

New research has found that one species of the enormous Goliath beetles has been almost wiped out by the west African cocoa industry and, to a lesser extent, by the international trade in dried insects.

One of Africa’s giant beetles is just one step away from extinction. New research has found that one species of the enormous Goliath beetles has been almost wiped out by the west African cocoa industry and, to a lesser extent, by the international trade in dried insects. Luca Luiselli, a professor of biostatistics and ecology at the University of Lomé (Togo), has researched threatened species in African forests for 30 years. He explains what has gone wrong and how the Goliath beetle could be saved.

The Goliath beetles (genus Goliathus) are among the world’s biggest insects. There are five different species. They grow up to 110mm long; males have Y-shaped horns and females do not have horns. The beetles are found in the rainforests of Sierra Leone, Liberia, Guinea, Côte d’Ivoire, Ghana, Burkina Faso, Benin, Nigeria, Cameroon, the Democratic Republic of Congo, Uganda and South Sudan.

Beetle larvae, or grubs, are omnivorous and likely scavenge on meat as well as debris of plants. This means they have an important role in moving nutrients throughout the forest ecosystem to nourish other plants and animals. The adult beetles feed only on the sap of a few tree species in mature rainforest areas.

The Goliath beetle is an excellent indicator of forest health: if they are abundant in a forest, it means the forest is in a good enough condition to support other species. But when their populations decline, this is an early warning indicator of emptying forests and eroding ecosystems.

I was studying reptiles under threat in west Africa’s forests with a team of ecologists from African and European countries. I realised that the Goliath beetles shared the same habitat and could also be endangered.

My team then began intensive face-to-face interview campaigns in communities to find out if local people had noticed fewer Goliath beetles about. These local people included hunters, farmers, snail and mushroom gatherers, and collectors of timber and other forest material. When they confirmed our fears, we decided to launch an in-depth research project. This shows that traditional ecological knowledge is very valuable in driving research decisions.

To start, we tracked the trees that were oozing sap because the adult (imagoes) beetles are known to feed on sap during the daytime. We then noticed which treetops they flew through every morning. We returned at night to collect and measure them before releasing them back into their natural habitat.