Giant Fijian Longhorn Beetle (Xixuthurus heros)

Giant Fijian Longhorn Beetle (Xixuthurus heros)

The Giant Fijian Longhorn Beetle is the world’s second largest beetle, with specimens reaching up to 15 cm in body length.

Members of the genus Xixuthrus all have a similar appearance, with the main differences between them being their size.

Like other beetles, the Giant long-horn beetle has four wings whereby the outer pair (elytra) are modified into a stiff protective shell and cover up the inner membranous pair when the wings are not in use; two mouthparts are made up of two pairs of jaws: mandibles and maxillae) which are adapted for chewing; three pairs of legs; and has a long pair of antennae.

Distribution

Colo-i-suva, Navua, Natewa Peninsula, Savusavu and Taveuni.

 Giant Fijian Longhorn Beetle (Xixuthurus heros)

Giant Fijian Longhorn Beetle (Xixuthurus heros)

Habitat Ecology and Behaviour

The Fiji long-horn beetle belongs to the family Cerambycidae, which are wood-borers and feed on plants. They usually require a host tree in which to live and deposit their eggs into. It is not known if these beetles have a specific host tree species; however, these types of beetles tend not to be strongly host-specific or selective. It is interesting to note that an adult Fijian longhorn beetle was once hacked out of a dying mango tree (Magnifera indica); and that larvae have been found in a dead standing rain tree (Albizia saman). Both the mango tree and rain tree are introduced species. Recent field surveys by Wildlife Conservation Society and the Forestry Department have found giant larval tunnels averaging 5cm in diameter in buabua (Fagraea gracilipes), a threatened species of native hardwood that has a wide diameter of up to 80cm (Yanega et al., 2004).

The dull brownish colour of the Long-horn beetle allows it to camouflage on the bark of trees. The limited data available on the reproductive ecology of this species suggests that the larva, which is a delicacy in many Fijian villages, takes 12 years to grow and mature into an adult. Collection data of specimens suggests that adults are present all year round but are more common from May to September, and that they require intact native forests. Older as well as recent specimens have been collected from or adjacent to natural forest areas and it has been suggested that they prefer to live in the tall big trees of Fiji’s lowland rainforest, particularly the lowland rainforest areas, which have been the target logging areas for many years.

Because of the rarity of the adults of this species, there has been no detailed ecological research conducted on it. In 1988, an adult male while flying to a light source around the Navua area was captured by natural historian, Paddy Ryan; while the beetle was kept in captivity, several observations were made. It was usually active at dusk, there were no observations of the beetle feeding while in captivity and its wings made a very loud whirring noise when flying. Because it was an adult, it was able to defend itself in having a large and powerful jaws; when grabbed by the pronotum, the beetle raised its head and attempted to entrap the ‘predator ‘between its antennae and pronotum; it produced a loud hissing noise when picked up: a feature that is common in members of this family as an aggressive or sexual method of interaction and to indicate alarm.

Threats

A single larva takes 12 years to reach adulthood, and this is when it is most sought after as a delicacy. The harvest of the larvae means that fewer larvas reach adulthood, and therefore a decrease in the population.

Many areas with lowland rainforests in which the longhorn beetles seem to live have been logged, and many big trees have been removed. The continuous logging and cutting of these trees, in addition to continued harvesting of the Fijian Longhorn beetle are a threat to the survival of this species. Additionally, the there is relatively little known of the beetle’s host tree species. A native tree, Trichospermum richii(mako) is suspected to be its host plant as well as Myristica castaneifolia (kaudamu) and Palaqium fidjiense (bua).

Conservation Status

The three species in this genus have recently been submitted for inclusion into into Fiji’s National protection list through the Endangered Species Act, based on the rarity and potential vulnerability for extinction. However, the level of protection awarded to this species is yet to be recognised as they are not in the current Endangered Species Protection Act (2002), nor the IUCN Redlist of Threatened Species, nor the CITES Appendices.

In 2007, a USP entomologist, Mr. Sunil Prasad came upon an internet auction of our Long-horn beetle. This confirmed that there is indeed an international trade for our Long-horn beetle in existence, but we are limited in our means to protect it both from trade and extinction because of harvesting and habitat destruction. Research into the distribution, habitat and ecology of the Giant long-horn beetle is currently being conducted at the University of the South Pacific as a PhD. Research project by Hilda Waqa.

Remarks and Cultural Significance

The three species in this genus have recently been submitted for inclusion into into Fiji’s National protection list through the Endangered Species Act, based on the rarity and potential vulnerability for extinction. However, the level of protection awarded to this species is yet to be recognised as they are not in the current Endangered Species Protection Act (2002), nor the IUCN Redlist of Threatened Species, nor the CITES Appendices.

In 2007, a USP entomologist, Mr. Sunil Prasad came upon an internet auction of our Long-horn beetle. This confirmed that there is indeed an international trade for our Long-horn beetle in existence, but we are limited in our means to protect it both from trade and extinction because of harvesting and habitat destruction. Research into the distribution, habitat and ecology of the Giant long-horn beetle is currently being conducted at the University of the South Pacific as a PhD. Research project by Hilda Waqa.

References

Yanega et al. (2004);
Ryan et al. 1989;
Graeffe (1986);
Prasad et al. (2007);
Waqa, H (personal communication).

Front Page Photo by: Douglas Yanega