Location: Rangiotu, Manawatu [North Island, New Zealand]
December 31, 2012 6:54 pm
Every summer we have a plague of lax beetles and it is driving me to the point of wanting to move house. We have all suffered the painful blisters and just now we had to remove a large lax beetle from out 11 month baby’s face. Ran inside and washed it with running water but still waiting to see what emerges. I know you do not endorse eradication but summers are rather unpleasant living in fear of these little bugs and I would really like some tips on how to control them and protect my family. We live in the country and work, play and eat outside whenever the weather is fine and we enjoy our diverse selection of wildlife and insects. These beetles are something else and I am scared to let my young children play out on the lawn. Each morning I am sweeping up tens of these from the floors and decks around the house.
Signature: ? Pania Flint

Lax Beetle

Dear Pania,
We have to confess that we had no idea what Lax Beetles were until we began to research you submission.  We learned on Nature Watch that Lax Beetles are False Blister Beetles in the family Oedemeridae.  We also learned on Nature Watch that “Adults contain the toxic cantharidin in their corporal fluids as a defensive mechanism; several species show brilliant and metallic blue, green, gold or coppery, often combined with yellow, orange or red, aposematic colourations. In temperate regions, adults are mainly polyphagous pollen and nectar-feeding, and diurnal in activity. In tropical areas, most are nocturnal and are attracted to light.”  We then learned the identity of your beetle, the Striped Lax Beetle,
Thelyphassa lineata, on Project Noah.  Photos can also be found on the Australian government page PaDIL.  The New Zealand Landcare Research website indicates:  “Attracted to lights  Grubs found in rotten wood  Adults probably feed on pollen and nectar.”  We do not give extermination advice, but you might be able to control the numbers of Lax Beetles by controlling their needs.  Do not keep outdoor lights on at night and try to secure window screens so they cannot get indoors at night.  Remove all rotting wood from the vicinity and try to determine which pollen producing plants the adults are attracted to and remove those plants from your yard.

Thank you for your quick response and the useful links.
We have done a bit of research in the past and have come up with more-or-less what you have said. We do also have the spotted lax beetle here and I am pretty sure we have the odd “Dark-patch lax beetle” as well. Haha – There is nothing “false” about the blisters they produce. The biggest problem is that we are surrounded by pine trees and that is, presumably, where they breed. We can not identify any nectar producing plants that would attract them to the garden, except lemonwood trees but they are not flowering at present. The lights of the house at night attract them for sure, so we keep windows and doors closed after dusk. They may be attracted to the lucerne flowering in the paddock.
I don’t think any of the more colourful varieties of blister beetle are present in New Zealand.
They are definitely nocturnal here (although we are in a temperate, not tropical location). They fly at night, starting in the early evening, (not sure about feeding patterns), during the day they hide in shady, damp areas, and are often in the folds of the sun umbrella at the outdoors table or in the crevices of wooden structures. They do not usually fly during the day and are usually found on their backs with legs moving when I sweep them up off the floor and deck in the morning. If turned right way up, they walk quickly along floors and walls and people. If knocked off of high object, they usually just fall down to the ground and start walking rather than fly off.
If a lax beetle lands on you the most important things to do are: Do not squash it – Do not rub it or brush it off slowly, use a very quick flick to get it off, hopefully before it can release the toxin from its joints. Then wash the area of skin under plenty of running water. That seems to work in most cases for us and my baby’s cheek seems to be OK after following the above procedure. Where we have problems is when we do not notice the beetle on the body and then maybe accidentally squash it a bit. We have often been blistered while sleeping. Apparently they are quite toxic if accidentally ingested. That is unlikely due to their large size, but a baby might pop one in his mouth out of curiosity. They can be eaten by stock, e.g. in hay but we have not noticed any problems with our stock.
On the positive side, while the blisters can develop into fairly large, painful erosive lesions that take several weeks to heal, there does not appear to be long-term scarring. The blisters themselves are not painful, it is the erosion left after the blister pops and skin lifts that is painful. I had a large blister across my chin three years ago. It took about 2 months to heal but there is no residual scarring now and my older son had a blister approx 7cm diameter on the top of his head when he was a 3 month old baby that healed up fine.
It would be useful to know:
What is the flight distance of an adult?
What do the nymphs or larvae look like? (I haven’t found any pictures on the internet)
What is the exact life-cycle.
Are there any specific plants that they feed on?
How quickly does the cantharidin toxin break down and can it be released from dead beetles?
The published literature seems to be limited.
Thanks again

Hi Pania,
This will take considerable research.  For the moment, we will feature your question and we hope one of our readers might be able to assist in this matter.

Location: New Zealand

10 Responses to Request for Information: Lax Beetles from New Zealand cause contact dermatitis!!!

  1. Tony says:

    The toxin is quite stable and slow to break down, and yes it can be released by dead beetles – dead beetles in hay can poison stock.

  2. Stacey says:

    We also have these lax beetles which have only just started coming around for a few weeks through january in the last five years (we never had any before then). They are a real niusance and our doctors couldn’t even tell us what had caused the blister – they told us it was sunburn. I only discovered the cause via google and noticing the arrival of these beetles. they definately come out at twilight and then disappear again once it is dark. I would love to know what they are feeding on or living in so we can erradicate them. As they are new to our area, they don’t belong here, they are very frustrating and dangerous to our young children also.

    • bugman says:

      You did not provide a location, but it is our understanding that Lax Beetles are native to both Australia and New Zealand. We do not provide extermination advice.

      • Stacey says:

        Hi there
        Sorry, I reside in Whirinaki, South Hokianga, Northand. I understand why you would not want to erradicate these if they are native to NZ, but if they are new arrivals to our area, how do we know they are not disturbing the eco-system and the insects etc that have been here all along??

      • Louise says:

        Hi there,

        These are not native. They are Australian and was introduced to NZ in the 1930s…

    • Bugger says:

      These bugs are from Australia, introduced to NZ in 1931. They are just now spreading very quickly around NZ. They breed in Mangrove swamps apparently

  3. Melissa says:

    The last 3 days me & my family have been staying in our family Bach in Kaimaumau… These bugs turned up every night as soon as the sun went down and stayed around for bout 2 hours. It was like a swarm of them! You couldn’t walk outside without getting attacked by about 20 at a time. We are all covered in blisters! They weren’t around last year… Would love to know where they have come from and why there is so many as soon as the sun goes down!?

  4. Clint Rissmann says:


    We have a lot of lax beetles here in Southland, New Zealand. Our property is surrounded by native forest and I have noted 6 or 7 beetles at a time. Often on the ceiling or window sills. I recently have been ‘stung’ by one. Fold of my elbow with a classic Kissing pattern to the blistering. Very symmetrical. Started as a small spots in the morning before developing large > 10 mm blisters by midday. I did not realise that we had these sort of beetles in NZ and had falsely assumed a whitetail spider bite. However, have never seen a whitetail in Southland before but have seen a heap of Lax bettles.



  5. Page Nolan says:

    I live in southern Arizona and I have been seeing a lot of beetles this year. Many of them are blister beetles and kissing bugs. Both can be dangerous. I have some native geckos as pets and I keep a light on at night so I can catch their meals. I dont wanna feed them anything that would do them harm so everytime I see a new bug I take it’s picture and reverse image search it. I was suprised that the one I just found looks and acts like this one from New Zealand. The blister beetles here are usually red and black but I’ve seen many different colors and patterns this year. And it’s barely the end of April! I’m thinking it’s going to be worse come July.

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