Phoracantha semipunctata, the Australian Eucalyptus longhorn, is a species of beetle in the family Cerambycidae. Native to Australia, it has now spread to many parts of the world, including practically all countries where tree species of Eucalyptus have been introduced. It has been classified as an invasive pest species of Eucalyptus outside Australia.

Within Australia, Phoracantha semipunctata primarily seeks for decaying trees and branches which have been critically impaired due to natural disasters. In other regions of the world, it inflicts critical damage upon introduced Eucalyptus trees. However, the damage inflicted by Phoracantha semipunctata may be seen as a positive factor in some regions, as Eucalyptus trees that are introduced are seen as invasive plant species imposing harm on the natural environment.

Phoracantha semipunctata are typically dark brown & beige in colour and are approximately similar in size measuring at around 2.3cm long. They are primarily active during the more temperate initial dusk hours, and are found in populations within host trees, which are predominantly male-oriented. These host trees are determined according to the suitability of adult mating and oviposition, and the viability of larvae development.

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