Your Question: What are these swarming beetles in my garden?
The Discovery Centre has received many enquiries over the last few weeks about swarms of beetles in suburban gardens in and around Melbourne; they are Plague Soldier Beetles, Chauliognathus lugubris.
Plague Soldier BeetlesImage: Peter SaundersSource: Peter Saunders
This flattened, elongated, soft-bodied beetle has a thin yellow-orange stripe across the back of the pronotum. It has metallic olive green elytra (hardened forewings), covering most of a yellow-orange abdomen. The legs, head, antennae and rest of the pronotum are black and the beetle is usually about 15mm in length. This native species has earned its common name of the Plague Soldier Beetle not as a result of bringing or spreading any dangerous plagues, rather due to its habit of forming huge mating swarms.
The larvae of this species live in the soil and feed on soft bodied invertebrates, while the adults feed on pollen and nectar. The species is found across large parts of the country including urban areas and adults can be seen from spring through to autumn. During their mating periods they can appear in such large numbers that it is not uncommon for them to weigh down the limbs of weaker plants.
Their bright colour warns off predators as they are capable of releasing distasteful chemicals and would not make a good meal. For homeowners who may be hosting huge numbers of this colourful species, don't be too concerned, following the mating swarm the beetles tend to disperse.
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Hi Jeanne, we have checked with the Entomologist, and he has found no record of the Plague Soldier Beetle being harmful to horses.
Hi to all the people currently hosting populations of Plague Soldier Beetles. We understand some of you find their presence somewhat intimidating or annoying but try not to be too concerned. The beetles are native and don't bite. People want to know how long they'll be around and how to prevent them coming back. It seems to vary considerably with some people reporting them leaving in a couple of days and some reporting them staying for more than a week.
The Museum is not aware of any treatments to prevent them coming back. These beetles can be a positive in that they will be consuming things like aphids. People can try squirting them with the hose to move them on but as they are very focused on getting together and mating the easiest thing may be to let them get that done and then they'll move on.
Hi Janelle, I have been having a look at registered museum specimens for this species and you are correct that the majority of the records tend to be south-eastern Australia but there are some museum records of this species from south-eastern Queensland. In terms of moving them on that can be difficult as the females release a pheromone to attract the males. The sole purpose of these swarms is to mate and they are pretty hard to dissuade.
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Thanks for the info! I found it very helpful.