Question: This little beetle was sitting next to me on the tram this morning. What is it and where was it going?
Answer: The beetle on your tram was an Elm Leaf Beetle, Xanthogaleruca luteola.
An Elm Leaf Beetle, Xanthogaleruca luteola
Photographer: Alan Henderson, Source: Museum Victoria
One of the beautiful features of Melbourne is the avenues of planted trees, many of them featuring introduced species such as the Elms. Many Elm populations around the world have been devastated by Dutch Elm disease; at present this disease is absent from Australia but other threats to Melbourne’s beautiful, mature Elm trees include drought and the introduced Elm Leaf Beetle.
The Elm Leaf Beetle is a species of beetle from Europe; it was found on Victoria’s Mornington Peninsula in 1989 and has now spread to Melbourne and regional areas. It causes damage to Elm trees in its larval and adult form. The beetles are not borers but they cause damage to the tree by feeding on the leaves. In severe cases they can cause defoliation of the tree.
Elm Leaf Beetles are around 6 mm in length. They are attractive mainly yellow beetles with black stripes on their elytra (protective wing covers) and black spots on their thorax. As adults, Elm Leaf Beetles eat distinctive ‘shot-holes’ in the leaves. The larvae ‘skeletonise’ the leaves by consuming everything but the veins of the leaves.
Once the larvae are ready to pupate they move down the trunk of the tree to pupate in the soil or in any crevices in the bark of the lower trunk. One control method is to trap the larvae as they move down the tree trunk between mid December and February.
When the weather starts to get cooler the adult beetles can over-winter in peoples’ homes or cars. In spring, when the weather starts to warm up again, they re-emerge and start looking for Elm trees again.
People are often concerned that they have borers in their homes when they find large numbers of these beetles emerging in their homes. However, Elm Leaf Beetles will cause no problems to peoples’ homes; they just use them to stay warm and secure over winter.
Elm Leaf Beetles are often brought into the Melbourne Museum Discovery Centre for identification. I expect the beetle entered your tram accidentally. Or perhaps it came in on purpose - trams are certainly a wonderful way to travel to the many elm-lined streets in Melbourne.