Longhorn Beetle (Xylorhiza adusta)

I find longhorn beetles exceptionally charismatic. The long antennae (although some species have short antennae) easily distinguish this group from other beetles. And it is those long antennae, the large size of certain species including some really colouful patterned ones that have enthralled generations of naturalists. The Chinese has a very apt name for longhorn beetles: 天牛. It means ‘sky cow’. The long antennae reminding them of cow horns and ‘sky’, I can only, or would rather, assume refers to the beauty of these beetles that can only be heaven sent.

Longhorns are in the family Cerambycidae with about 35,000 described species worldwide. In larval stage they are mostly wood-borers and are thus considered pests in the forestry industry, especially so in western countries where introduced Asian species are considered invasive. But in their natural habitat, longhorns have an important role in the nutrient cycle in breaking down dying or decomposing woody plants. Most species can also feed on living trees. Adults feed mostly on young leaves and twigs.

Two recent species I saw. The first is Xylorhiza adusta from Sungei Buloh. It has a wide distribution in Asia, from India to China and down to Sumatra. Known host plants include Beautyberry trees (Callicarpa arborea and C. macrophylla); plant from the mint family (Premna pyramidata); Viburnum odoratissimum and Wrightia tinctoria: both a kind of small shrubby tree. All the above plants have not been recorded in Singapore but species from the same genus can be found here.

I still can’t identify the other longhorn except that its probably Acalolepta rusticatrix. I saw it, of all places, at a pedestrian bridge along Lornie Road.

Alfred Wallace was a beetle lover and collected 132 longhorn species from Singapore. His collections form the basis of our local knowledge and today Singapore has an estimated 220 plus species although a significant number might already be nationally extinct due to habitat loss. Current information on Singapore longhorn beetles diversity is still sketchy with many knowledge gaps to be filled. A giant step forward has been taken with this website (http://www.singaporeinsects.com/index.htm) created by the industrious Cheong Loong Fah.

Pictures taken at: Lornie Road, March 2010; Sungei Buloh Wetland Reserve, June 2010.

References:

Chong, K. Y., H. T. W. Tan & R. T. Corlett, 2009. A Checklist of the Total Vascular Plant Flora of Singapore: Native, Naturalised and Cultivated Species. Raffles Museum of Biodiversity Research, National University of Singapore, Singapore. 273 pp. Uploaded 12 November 2009. http://rmbr.nus.edu.sg/raffles_museum_pub/flora_of_singapore_tc.pdf.

Duffy, E. A. J., 1968. A Monograph of the Immature Stages of Oriental Timber Beetles (Cerambycidae). British Museum (Natural History), London.

Ek-Amnuay, P., 2008. Beetles of Thailand. 2nd Edition. Amarin Printing and Publishing Public Co., Ltd, Bangkok.