It's still a mystery why the green and yellow Plague Soldier Beetle, found in temperate southeastern Australia, occasionally builds up to massive numbers.

An unfamiliar yellow and green beetle with a soft body may be a source of curiosity if it turns up in your garden. Will it eat the plants, or bite people? A dozen of the beetles together might start to cause concern. But ten thousand of them festooning a tree are bound to raise alarm. Yet the insect in question won’t harm either you or your plants.

Image of a Plague Soldier Beetle

A Plague Soldier Beetle, Chauliognathus lugubris

It is still something of a mystery why the Plague soldier beetle (Chauliognathus lugubris), a native species found in temperate southeastern Australia, occasionally builds up to massive numbers. Its grubs live in the soil, feeding on other small creatures. The adult beetles don’t seem to eat the plants they settle on, although the sheer weight of a mass of them may break weaker twigs. What they are more interested in is sucking nectar from flowering trees, and copulating.

The bright colours of Chauliognathus are a warning to any predator thinking of taking a swipe at one, as they exude a white viscous fluid from their glands that repels any predators thinking of getting too close.

Close up image of the secreted fluid of a soldier beetle

A close up view of the secreted fluid (Image Victoria Haritos)

The soldier beetle also secretes the same chemical in a wax form to protect it’s eggs against infection.

Our researchers have recently found the genes that give the chemical its anti-microbial and anti-cancer properties, and were able to replicate the synthesis in the lab. This may one day lead to the development of new anti-biotic and anti-cancer related products.

Record a sighting on the Atlas of Living Australia

*UPDATE- Thanks to ‘br’ for leaving this video in our comments thread. We thought it was worth sharing. Prepare to be creeped out by these crawlies…




  1. They are covering nearly everything in my very large garden – including the lawns – and definitely doing damage to young shoots and blooms. I have started spraying them with malathion and “Astound” but am concerned I may be poisoning birds that might eat the dying insects. Is this likely?

    1. the insects secrete a substance that repels the birds from eating them…though if they did eat them you wouldn’t have an issue

      1. Just wondering what you mean by “wouldn’t have an issue”. Do you mean that the chemicals I spray with are not toxic to birds or that it wouldn’t matter if birds were poisoned?!

    2. yes.. you will kill the birds… just hose them off.

  2. Is there any way of getting rid of them quicker? I cant hang out the washing, they are very annoying. Im Northside of Canberra.

    1. If there is a flowering tree or shrub in the vicinity that the beetles are being attracted to, you could get rid of it. Otherwise there is nothing you can really do except wait for them to disperse.

      Regards, Kim.

      1. I am pretty certain that they can sting you. I was sweeping up and not wearing shoes. I felt a sting on my foot and soldier beetles were the only living creature in the immediate area. I expected to find a bee minus its stinger as the pain was rather severe and one day later my foot is itchy and swollen. These beetles come to the front of our house every year around March-April and have done so for the 40 years I have lived here. Only our house, nowhere else.

    2. After 2 years I have worked out how to get rid of them. In the morning get out and shake the trees they are in (they love my cotoneaster) and they fall to the ground. Then, stomp on them, spray with Mortein or Pea Beau, rake them up, shovel into a big bag , spray with mortein, seal bag and dispose of. Repeat the next morning(s)


      1. wow Geoff, the eucalypt and bushes I have seen them populate are not harmed by the invasion of several days so why bother exterminating them. I am stoked that there is a native species that doesn’t harm plants OR people. A good species to attract people into observing “bugs” without harming or being harmed I reakon.

      2. G’day folks they are thew early advance party of an intergalatic higher life foce comming to observe how cilivised we humans are so Geoff lokks like you might ahve blowen it for us uncilivised humans. On another not the bennifits of thes elitle bugs seams enourmous bit like the pesky mozzie they are the pollanators of Upmartia a native small tree related to the magnolias. It seems ther is more research needed to see what roal these bugs play in our life cycle. I have noted them over the years in various location, they appear to be arouns most seasons. Pete Ward Merriwa NSW

  3. We have a swarm in our courtyard in Port Melbourne. Can you pls tell me how long they live and will they go away.

    1. I can’t say how long they will stay around. My prediction is that they will disperse within a week, although some stragglers might take longer to leave.
      Kim Pullen

      1. Here’s what I know- most people claim they have a Gumtree in their yard where these insanely annoying beetles are. I have 2 huge (over 8 meter tall) gumtrees in my backyard. From end November 2013 I had barely any flying around the tree- Until last week (end Jan 2014) I now have my whole veggie patch, trees, bushes, grass and kids trampoline so widely covered that you look out my Window and see black movement on everything- not one bit of green showing.
        They do bite- as my almost 2 year old found out, which only happened an hour ago but I believe no reaction.
        They have been around for months- and my tomatoes were looking fabulous until last week- now half my plant is dead.

  4. We are in Dandenong North Victoria and have tens of thousands of them on an ironbark. Having read your information I am now not concerned about them, however would love to know how long they will hang around? Thanks so much for the information.

    1. My prediction is that they will disperse within a week, although some stragglers might take longer to leave.
      Kim Pullen

      1. I have had them living in a tree in my front yard in huge quantities they have been there for more than a month and don’t seem to be going anywhere.

  5. Thank you for your article on Soldier Beetles. If the beetle is interested in sucking nectar from flowering trees why are they ALL over the ground and over plants/weeds etc. which have NO flowers on them? I am sure the beetles have caused damage and the early drop/browning off of petals from my rhododendrons and azaleas. (I live in Kinglake West, Vic). How long will this “plague” last? Thank you. Sue M.

    1. I can’t say how long they will stay around. My prediction is that they will disperse within a week, although some stragglers might take longer to leave.
      Kim Pullen

    2. The type of damage beetles cause when they eat foliage or petals is characteristic – they eat holes or bite bits off the edge. This type of damage has never been associated with Soldier Beetle swarms, so I said in the blog that the beetles ‘don’t seem to eat the plants they settle on’. I don’t know what may have caused the ‘early drop/browning off of petals’ that you describe.
      Kim Pullen

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