Coconut rhinoceros beetle adults chew big holes through the growing tops of palm trees to feed on their sap, making distinct zig-zag shaped cuts in their leaves. This is a big beetle to battle, but Frankie knows that cleaning up palm debris and compost piles prevent its larvae from growing inside them. He's on the lookout!
Printable Field Guide: PDF
Scientific Name:Oryctes rhinoceros
Description: Coconut rhinoceros beetles are quite large (1 ¼ - 2 ½ inches) and shiny black. They are called rhino beetles because both males and females have a horn on their heads that looks like a rhino horn! The male’s horn is larger, and they sometimes use these horns to battle one another for food or mates. Larvae of the CRB are large, off-white grubs with brown heads.
Native Range: South and Southeast Asia, from Pakistan to the Philippines
Introduced Range: CRB has been introduced throughout the South Pacific, and is now found in American Samoa, Bismarck Archipelago, the Cocos Islands, Fiji, Guam, Manus Island, Mauritius, Micronesia, Papua New Guinea, Saipan, Tonga, Wallis Island, and Western Samoa. It has most recently been discovered in Hawaii.
Habitat: Natural forests, palm plantations, and planted landscapes.
Host Trees: Adult CRBs attack coconut, oil, and date palm trees. They also attack other species of palms, such as Hawaii’s only native palms, the endangered fan palms, or Loulu. CRBs also sometimes feed on Pandanus (screwpine) trees, banana trees, sisal, sugarcane, and pineapple.
The Facts: This big bug is bad news for palm trees! The adult beetles burrow into the bases of palm fronds to drink the tree’s sap. When CRBs burrow in to feed, they create large holes near the top of the palm’s trunk, which can allow other bad bugs and fungi to enter and damage the tree. Because palm trees only grow from one central point at the very top, the beetles’ burrowing can also damage the tree’s ability to make new leaves and may kill it. They chew through the new palm leaves that are folded up within the top of the tree, making “v” shaped cuts in the leaves when they extend. Unfortunately, when one beetle finds a tasty tree, it calls in its friends for a mass attack!
Female rhino beetles love to lay their eggs in rotting wood, compost piles, and manure heaps, and the larvae eat this dead material when they hatch from the eggs. Coconut palm logs that have fallen to the ground are especially good places for CRB larvae to hide and feed. In areas where CRB is found, it is important not to move piles of branches or yard waste, or you could be taking rhino beetle grubs with it!
Natural enemies of the CRB include rats, pigs, other beetles, birds, and ants. In the CRB’s native range, a fungus and a virus are present in the environment that make the larvae sick and control their numbers, but these natural enemies are not present where this bug has been introduced. Beetle battlers in Guam and Hawaii are trying very hard to rid their island nations of CRB through a combination of trapping adult beetles and cleaning up piles of tree waste that may breed more of these bad bugs.