Beetles are the world’s most diverse insect, and with over 360,000 different types, there are more different beetles than any other animal. Rainforest beetles are exceptionally diverse containing the largest beetles on Earth, such as the goliath beetle of tropical Africa or the titan beetle of the Amazon Rainforest. Below are some interesting rainforest beetles you may see in the world’s tropics:
Rainforest Beetles – Ground Beetles (Carabidae)
You can usually identify a ground beetle by its flattened shape and strong robust legs for running. All ground beetles are terrestrial and most are predators. One of the favourites are the tiger beetles with their aggressive appearance and strong biting mandibles. Tiger beetles (Cicindelinae) are such superb hunters that they can even hunt down flying prey.
Longhorn Beetles (Cerambycidae)
The most distinguishing feature of these beetles is their large antennae, sometimes reaching several body lengths. They have strong jaws, large searching eyes, strong robust legs and powerful claws. One species you may see in the Australian wet tropics is the poinciana longhorn (Agrianome spinicollis). Poincianas are large beetles about 6 cm long with khaki wing covers. On the other side of the world, poincianas are dwarfed by the Amazon Rainforest’s titan beetle (Titanus giganteus). The largest was 18 cm (7 inches) long making these the largest beetles on Earth (photo above). Their jaws are said to be strong enough to snap pencils, although the adults themselves do not feed.
Stag Beetles (Lucanidae)
Stag beetles are another clearly distinguishable group. You know it’s a stag beetle if it has two antler-like appendages on its front. The male and female beetle look very different as they have different shaped jaws. The males are often larger and antler like, giving the beetles their distinguishable common name.
Stag beetles have strong front legs adapted for digging in wood. Some are very attractive with metallic iridescent colours, but the majority are earth coloured camouflaging this large beetle from predators.
Stag beetles are active at night with adult beetles eating young plants, ripe fruit, and tree sap. A favourite in the Australian Wet Tropics is the Mueller’s stag beetle (Phalacrognathus muelleri), although you have to be very lucky to catch a glimpse of this impressive beetle. They are around 5 cm (2 inches) and have an impressive metallic casing. Both males and females display the family familiar staghorns.
Dependent on species, scarabs can vary in size from either very large like the goliath beetle, to tiny Aphodius scarabs at about 2–8 mm. You can identify a scarab by the protective plate covering their jaws. Scarabs always have a stocky body and they can be brightly coloured with some males having large rhinoceros-like horns.
A common large species in the Australian Wet Tropics (about 6 cm long) is the Australian rhinoceros beetle (Xylotrupes ulysses) with its pitch black casing and impressive rhino-like horn. When this beetle is stressed it lets you know by giving out a loud hiss. The larvae are also impressive at about 6 cm long.
In the Amazon Rainforest, you may see a colourful metallic green species in the genus Oxysternon. These will follow you through the jungle and try to land, as they do other large mammals, waiting for their prized dung. Because the beetles are so efficient at locating manure and large mammals, other species use them for transport. These beetles are carriers of mites and when the beetle lands, mites begin to disembark their insect-plane to feed on freshly deposited dung.
The largest scarab is the goliath beetle (genus Goliathus) from tropical Africa. These beetles have powerful claws for climbing trees and attractive patterned colouration over their robust casing.
Click Beetles (Elateridae)
Adult click beetles have a specially sculpted pit in their exoskeleton where, with a certain bending of their body, a spine tentatively rests on the pit-edge. The spine then slips into the cavity with such force that the beetle is catapulted into the air to escape predators. Most click beetles feed on plant material but some prey on smaller animals.
Rainforest Beetles – Jewel Beetles (Buprestidae)
You can identify a jewel beetle by their usually flattened and elongate body. They have large eyes with short antennae and when defending themselves retract their legs against their body. Adults usually feed on nectar and they can be very brightly coloured. One of the common and attractive large beetles in the Amazon Rainforest is the ceiba borer (Euchroma gigantea) pictured above. These are the largest jewel beetles in South America. You can spot Ceiba borers on tree trunks warming themselves in sunlight.
The most species rich and diverse of all the rainforest beetles, most entomologists have a secret soft spot for weevils, while most crop farmers don’t (weevils are a major economic pest). Weevils are the gonzo Muppet of the rainforest beetle world with their long snouts lengthening their mouth parts. In order to fit in this group, beetles must have noticeable elbows in their antennae. If not, the beetle is probably a related beetle in one of the smaller families. You are sure to see weevils as you explore the world’s rainforests.