The African Goliath beetle (Goliathus goliatus) is a marvel of nature, residing in the rainforests of central and western Africa. These beetles are famous for their size and distinctive behaviors.
The name "goliath beetle" is an obvious reference to the biblical giant Goliath due to the large size of the beetle. Goliath beetles refer to any of the six species of beetles in the genus Goliathus. As their name implies, goliath beetles are the largest beetles in the world.
They are members of subfamily Cetoniinae, within the family Scarabaeidae. There are up to 30,000 species of scarab beetles worldwide. All 6 species of goliath beetles are native to Africa.
Their nocturnal lifestyle, remarkable physical attributes, and crucial ecological roles make them a fascinating subject. However, they’re threatened by habitat loss from deforestation, underscoring the need for urgent conservation efforts.
A female Goliathus cacicus, one of the six species of Goliath Beetles.
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Physical Characteristics
The adult African goliath beetle has a stout, oval-shaped body, which, like that of other insects, is made up of the head, the thorax, and the abdomen. The beetles, residing in the central and western African rainforests, are a marvel of nature due to their immense size and distinctive behaviors.
The adult African goliath beetle remains among the largest of insects, ranking closely with the hercules beetle (Dynastes hercules), the titan beetle (Titanus giganteus), and the cricket-like giant wētā (Deinacrida).
Size and Weight:
- Some specimens reach lengths of up to six inches (15 cm).
- Some specimens weigh as much as 3.5 ounces (100 g).
- They generally weigh about 40-60 grams (1.4-2.1 ounces).
The largest and heaviest insect in the world, the larva of which is one of the heaviest insects in the world. Although smaller than its substantial larval form, the adult African goliath beetle remains among the largest of insects.
The bulky bodies of Goliath beetles are composed of a thick and hardened exoskeleton, which protects their organs and hindwings. Like most beetles, they possess reinforced forewings (called elytra) that act as protective covers for their hindwings and abdomen.
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Goliath beetles measure from 60-110 millimetres (2.4-4.3 in) for males and 50-80 millimetres (2.0-3.1 in) for females, as adults, and can reach weights of up to 80-100 grams (2.8-3.5 oz) in the larval stage, though the adults are only about half this weight.
The males can measure as much as 6-11cm (2.4-4.3 in) as adults, while females are typically between 5-8cm (2.0-3.1 in) in length. The largest of this is the G. orientalis, while the smallest species in the giant beetle genus is the G. albosignatus. In addition to these, there is a rare species known as G. atlas. This is only formed when a crossbreed happens between G. regius and.
Distinguishing Features:
- Males are larger than females and can be distinguished by the presence of a Y-shaped horn on their head.
- Females have a wedge-shaped head used for digging.
- The beetles have three pairs of legs with sharp, five-segmented claws that they use to climb trees and scalloped front tibiae.
Males have a Y-shaped horn on the head, which is used as a pry bar in battles with other males over feeding sites or mates. Females lack horns and instead have a wedge-shaped head that assists in burrowing when they lay eggs.
They have six legs and sharp claws, which are used for climbing trees. The head of the female goliath beetle is typically wedge-shaped, and this makes it easy for them to burrow through soil.
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Coloration:
- Color patterns of the African goliath beetle can vary between males and females.
- Most individuals have a white promontum (the upper plate of the prothorax, which is the region immediately behind the head) dramatically striped with bold black lines and chitinous wing covers (elytra) that are rusty brown in color.
- Some have white and black elytra.
The coloration of the insects in the Goliathus genus depends on their species. Coloration may also vary between male and female members of the same species. Typically, the color is a mix of black, white, and brown. For the G. goliatus, the color is predominantly black with white stripes. They’re the only species in the genus with a reddish coloring on their back. The G. regius and G. orientalis are mainly white with black spots or patches. G. cacicus is mostly brown with black and white spots.
Polymorphic populations of the beetle, consisting of a brown morph and a white morph, are found in Benin, Nigeria, and Cameroon. Collectors particularly prize the white morph, which is in marked decline.
Wings:
- The elytra cover large, black or brown, leathery wings.
- These inner wings, but not the elytra, are used for flying.
Goliath beetles have two sets of wings, but only the inner wings are used for flying. The outer wings form a thick chitinous exoskeleton called elytra. This covering protects the beetle’s inner wings and abdomen.
Only the hindwings (which are large and membranous) are actually used for flying, while the elytra are kept completely closed; flying with closed elytra is universal among cetoniine scarabs but rare in other beetles. When not in use, the wings are kept completely folded beneath the elytra.
Due to their large chitinous outer wings, it might seem like goliath beetles cannot fly. However, they have soft inner wings which are used for flying.
Dog with Flying Goliath Beetle
Larval Stage
The larval form of the African goliath beetle (Goliathus goliatus) is one of the largest larva of any insect, weighing 80-100 grams (2.8-3.5 ounces), about the weight of three or four alkaline AA batteries.
The larval form of the beetle is a massive, bratwurst-sized grub. At its peak size before pupating, it weighs 80-100 grams (2.8-3.5 ounces) and can have a body length of 114-150 mm (4.5-5.9 inches).
The larvae of goliath beetles consume as much protein within the soil or plant and animal matter as possible and therefore reach an extremely large size. Some larvae of goliath beetles can reach up 250mm in length and are some of the heaviest insects in the world.
Goliathus larvae are somewhat unusual among cetoniine scarabs in that they have a greater need for high-protein foods than do those of most other genera. Pellets of dry or soft dog or cat food (buried in the rearing substrate on a regular schedule) provide a suitable diet for Goliathus larvae in captivity.
However, a substrate of somewhat moistened, decayed leaves and wood should still be provided in order to create a suitable medium for larval growth. The young stage larvae (1st instar) will eat some of this material.
Habitat and Distribution
All species of goliath beetle are found in Africa. They typically live in locations with warm climates in southeast Africa. They may also be found in tropical and subtropical regions as well.
In places where they’re found, these giant beetles live in dense rainforests. Found in the rainforests of central and western Africa, Goliath beetles live in rotting logs and fallen trees.
Goliath beetles are native to the tropical forests of Africa. Specifically, they inhabit lowland and mountainous tropical forests where there is plenty of vegetation and high humidity.
Goliath beetles can be found in many of Africa's tropical forests, where they feed primarily on tree sap and fruit. They live in tropical and subtropical rainforests in the southeastern region of Africa.
Diet and Behavior
African goliath beetles are omnivores. Adults have sharp jaws, which they use to consume primarily sap and fruit. They climb trees and forest shrubs and can also be found in rotting logs and under forest litter.
Adult goliath beetles typically have a diet that consists predominantly of foods with high sugar. Tree sap and rotten fruits form a major part of their diet. They typically use their sharp claw-like jaws to break tree barks and fruits.
The adult beetles feed on materials rich in sugar, especially tree sap and fruit. They are only found in Africa. They typically live in locations with warm climates in southeast Africa. They may also be found in tropical and subtropical regions as well. In places where they’re found, these giant beetles live in dense rainforests.
Their mouths typically have a wooly area that looks like a paintbrush. Juveniles typically have a different diet which includes plant matter, dung and animal remains. The larvae grow rapidly, feeding on decaying plant matter, dung, and decomposing animals in the soil.
Given that they require a diet rich in protein to reach their large size, they may also be predators of other species’ larvae and perhaps even cannibalistic. Goliath beetles tend to eat food that is high in sugar like fruits, as well as dung, and dead animals.
Males frequently fight other males for mates or feeding sites using their forelegs and distinctive horns. Adult males are highly aggressive and territorial, defending tree trunks and fruiting bodies. The long horns are used as weapons in these fights, and the beetle with larger horns typically wins.
Adults employ a ‘sit-and-wait’ strategy while foraging. They remain stationary on a tree trunk or fallen log, waiting for food to become available. When they detect ripe fruit or sap flows, they rapidly dig into the food source.
Life Cycle
The life of a goliath beetle consists of 4 life stages. Usually a female lays her eggs in small depressions or burrows in damp soil or rotting wood. The eggs hatch into larvae during the rainy season and burrow further into the substrate.
After mating females lay their eggs in soil or decaying plant matter. The eggs hatch as grubs, and, like other beetles, the insects undergo complete (holometabolous) metamorphosis, meaning their life cycle consists of egg, larva, pupa, and adult.
The larvae develop into pupae underground and then emerge from the soil as adults. Adults live about three to six months in the wild.
Goliath beetles undergo complete metamorphosis with four life stages - egg, larva, pupa, and adult. Adult female beetles lay about 20-50 white, spherical eggs in decaying logs. Larvae emerge from eggs and immediately burrow into decaying wood to feed.
The larvae then change into pupae, which are inactive until the ground becomes damp again. Here the adults hatch and leave their burrows in search of a mate.
When maximum size is reached, the larva constructs a rather thin-walled, hardened cell of sandy soil in which it will undergo pupation and metamorphose to the adult state. Once building of this cocoon is completed, the larva transforms to the pupal stage, which is an intermediate phase between the larval and adult stages.
During the pupal duration, the insect's tissues are broken down and re-organized into the form of the adult beetle. Once metamorphosis is complete, the insect sheds its pupal skin and undergoes a period of hibernation as an adult beetle until the dry season ends.
When the rains begin, the beetle breaks open its cocoon, locates a mate, and the entire life cycle starts over again.
The pupal stage lasts around 1 month. Adult beetles emerge from pupae in midsummer, June-August. Reproductive maturity is reached in 2-4 weeks after emergence. Mating occurs at night on tree trunks where males grasp females with forelegs to mate. Females lay eggs soon after mating and then die shortly afterwards. The adult lifespan is only 3-6 months.
A Goliath Beetle larva.
Ecological Role
As with most beetles, goliath beetles are an important part of the ecosystem. Both the larvae and adult beetles provide food for a large number of predators, maintaining a healthy food chain in that environment. Their burrowing underground helps aerate the soil as well as providing shelter for other insects. They also help remove decaying plant and animal matter from their habitat.
Goliath beetles play an important part in a rainforest’s ecosystem, helping to pollinate plants and providing a food source for other animals, like birds and monkeys.
