The Goliath beetle, native to the tropical forests of central and western Africa, is consistently ranked among the world’s largest and heaviest beetles. Belonging to the genus Goliathus, these insects can reach lengths of over four inches, with males often displaying a pronounced Y-shaped horn on their head. The life cycle features a dramatic change in nutritional needs, with dietary requirements shifting completely across its two primary feeding stages. Understanding what a Goliath beetle eats means examining the distinct sustenance necessary for the adult’s energy maintenance and the larva’s massive growth.
The Adult Diet: Sap and Sweet Fruits
The diet of the mature, winged Goliath beetle focuses on readily available sources of sugar to fuel its active lifestyle. Adult beetles do not eat for growth, but rather for maintaining the high energy levels needed for flight, mating, and other survival behaviors. Their nutritional intake consists primarily of sugary liquids found in their native habitat, which they access using mouthparts adapted for non-chewing consumption.
These large insects frequently seek out tree sap, often targeting areas where the bark has been damaged to access the flowing, sugar-rich fluid. Fermenting tree sap is an attractive food source, providing an easily digestible energy boost. In addition to tree exudates, the beetles consume the pulp and juices of soft, overripe fruits that are abundant in the rainforest canopy.
Fruits like mangoes and bananas, once they have fallen and begun to ferment, offer a concentrated and accessible source of carbohydrates. This reliance on high-sugar, liquid foods ensures the adult beetle can sustain itself during its relatively short lifespan above ground. This specialization on sweet liquids also serves an ecological purpose, as it reduces competition for resources with the larva, which has a drastically different diet.
The Larval Diet: High-Protein Requirements for Growth
The larval stage of the Goliath beetle, known as the grub, differs greatly from the adult’s, requiring a massive intake of protein to achieve its enormous size. Unlike the larvae of many other scarab beetles that feed almost exclusively on decaying wood, Goliathus larvae demand animal protein to fuel their rapid development. These grubs can reach weights exceeding 100 grams and lengths up to ten inches before metamorphosis, making them the heaviest insect larvae in the world.
In their natural environment, this protein requirement is met by consuming decaying organic matter that contains animal remains. Researchers speculate that they feed on dead insects, small deceased vertebrates, or perhaps even other beetle larvae within their soil and detritus-filled tunnels. This high-protein diet is what allows the grub to store the necessary energy and mass to complete its transformation into the adult beetle.
The younger larvae, specifically the first instar (L1), will initially consume some of the surrounding decayed leaf and wood substrate, but this quickly shifts as they grow. By the time they reach the second (L2) and third (L3) instars, protein becomes the near-exclusive focus of their diet. This intense nutritional phase allows them to gain weight quickly, ensuring they reach the required pre-pupation size within the window dictated by the seasonal cycle of the tropical forest.
Replicating the Diet in Captivity
For those who raise Goliath beetles, replicating the distinct diets of both life stages is necessary to ensure their successful development and health. Adult beetles are easily sustained on commercially available beetle jellies, which are formulated to provide the necessary carbohydrates and nutrients. Alternatively, keepers use mashes of soft, sweet fruits, such as bananas or apples, ensuring they remove any uneaten portions to prevent mold and spoilage.
The larval diet requires careful management due to its high protein demands. To mimic the wild diet, keepers often use a specialized substrate of decaying wood and leaves that is heavily supplemented with protein-rich foods. Common substitutes for natural animal protein include commercial dog or cat food pellets, high-quality fish flakes, or specialized koi pellets. The protein content of these pellets is considered the most important factor for larval growth.
These protein supplements are often soaked in water to soften them for easier consumption and are placed directly into the larvae’s substrate. A meticulous feeding schedule is maintained, often involving feeding every two to three days, with uneaten food removed promptly to keep the substrate clean and prevent the growth of harmful bacteria or mold. This high-protein regimen is responsible for allowing the larvae to reach their maximum size and successfully complete metamorphosis.