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. Hi I live in Eltham, Victoria and they are swarming all over my zucchini’s, cucumbers and pumpkin. Does anyone know if they will they harm any of these plants? (they particularly love the zucchini plants.

  2. I live in the Blue Mountains near Sydney. We have had the beetles in our yard for three and a half weeks and they are buildingt in numbers. Have tried to out wait them and it doesn’t seem to work. Don’t want to take to spraying but with Christmas coming up I will have to.

  3. I made a video of them in Newcastle on some eucalyptus trees.

  4. Reply to Tim Buckley
    Hi Tim – bit hard to prevent them emerging over a 5 acre garden when I have absolutely no idea where they are laying! And even if I did know where they were I wouldn’t want to kill my dung beetles which, being on a farm, are very precious. I actually think selectively spraying just the one I’m trying to control (out of fear of even greater numbers next year) and being careful to avoid all others is the most logical approach.
    I have read more fully on alpha cypermethrin and am happy its not toxic to birds or to their fertility. The withholding period for fruit or crops sprayed for human consumption is only 24 hours so it must break down very quickly. I really believe I’ve done minimal harm to any other species while hopefully reducing my own population, but next year will tell!
    As a gardener yourself do you never have to resort to using sprays to control thrip and other pests? I have been gardening for over half a century and sadly find there are occassions when I can’t avoid their use – this was one as I couldn’t handle them in my hair, inside my clothes and one down my ear!.

    1. Hi Jennifer, I completely agree with your approach. I hope my original comment was not taken out of context. It was in relation to the majority that like to snuffle things without total understanding. Yes, 5 acres is a handful, and yes, I do spray things, both chemical and organic. I merely mentioned 2 types of control if people wished to attempt the control of the beetle. Now, for humours sake, I’ll give my opinion. I think they should be left alone. Even today in Sandringham they were all over us, in our hair, up the shirt, and up my shorts! I just blow them off me, and go about my work. Our female apprentice was not so agreeable, yet I had a discussion this very day about nature, and the more you understand it, the easier it is to make your decisions. One last thing, our experience has been that these little love makers last roughly a month, not a day, or a week.
      Happy gardening, and Merry Christmas

  5. Hello everyone – have had PLAGUE SOLDIER BEETLES for about 10 days and guess what ? Went out this morning and there are only a few stragglers left behind. NO sprays, insecticides etc were required just let Mother Nature do her thing !

    1. Hi Jenny, I thought that the other day but they came back 10 fold, I think they went under ground during the rain. I am away at the moment but on Friday they were in swarms covering my plants and walls. I understand we need to appreciate nature but they are unpleasant and a nuisance. I am worried when I come back they will be even worse.

      I’m over them!!

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