Acacia Longicorn Beetle - Penthea solida

FAMILY CERAMBYCIDAE

This page contains pictures and information about Acacia Longicorn Beetles that we found in the Brisbane area, Queensland, Australia.


Body length female 30mm, male 20mm

In mid summer, on those young Acacia trees in Mt Cotton, we found a few of those Longicorn Beetles. Some of them are actively moving around. When disturbed, some dropped onto the ground and played dead, some slowly flied away.



They appeared only in a short period of time in mid summer. A year later in the same area, we easily found a lot of them.



They have very long antennae, typically 11 segmented. They have obvious strong mandibles for chewing. Also notice its notched eyes and its antenna arising within the notch. This is the characteristic of all longicorn beetles.


On Dec 2008 we found them again on gum leaves. There were three resting on the stem. Two of them were mating.



Then we realized that the male and female are different size and colours. We found both of them individually and thought they were different species.




When looking at the beetle with the front view, we noticed why there are the round dome on each shoulder. Those domes mimic the eyes of a larger animal. The beetle spends long time on stem feeding plant skin. It will most likely encounter its predators, such as a bird, from above. The mimicking larger animal's face may scare away its predators. We have more information about face mimicking in this page.




This Longicorn is quite common in Brisbane.



They were found on different species of Acacia.





Reference:
1. Cerambycidae, subfamily Lamiinae - lifeunseen.com, by Nick Monaghan.
2. Specimen Image Index - Insect Reference Collection Database - ICDB, Western Australian Department of Agriculture.