Caterpillars dying

Tagged: ,

  • Creator
  • #50324



    I hope you can give me some information about this so I can try and do something to prevent the problem. I have planted lots of Milkweed, and have had big success with the Monarchs. I have documented. So far I have had 157 caterpillars hatching, the butterflies have been laying eggs continuously. Of these caterpillars 124 have made it to butterflies. Very happy about this.
    But the last few weeks several of the cats died; they gave off a black/brown liquid which I can see on the leaves and stems, and then either just fall off the plant and die, or they fall of and writhe about for hours and then die. It is awful to see. This seems to happen between 3rd and 4th instar.
    I have no idea what the cause is. My garden is totally organic, and I use no poison at all.
    Could you please advise on the cause of this?

    Thank you in advance
    Lindi Engelbrecht
    Gisborne NZ


Viewing 4 replies - 1 through 4 (of 4 total)
  • Author
  • #59084


    Lindi – we are now working with a scientist who is investigating Oe, a monarch parasite. You should hear about this in the e-news I’m putting together now…

    It may be helpful to you.




    I have a had a dreadful year (2019-2020) for cats and butterflies. I am vigilant re pests, but am always fighting ants, soldier bugs and wasps in my area.

    These are the things I have noted on my plants this year: –
    Eggs: lots laid, but appear to be going grey/silver and not emerging, not the usual colour
    Cats: those that have grown are not feeding well and have had some turn to black liquid
    Cats: when dying just fall off the plants ans writhe on the ground.
    I picked up 6 small cats to try to raise indoors, but they were all dead within 24 hours.
    Chrysalis: some forming but very discoloured and do not hatch – they eventually turn black and rot where formed.

    So, generally its been very upsetting year.

    Do you think I should pull out all my milkweed plants and start again?



    Hi Jacqui,

    Thank you very much for this insightful information. It actaully makes me feel better, because I was so worried it was due to something I had done wrong. I try to keep the spiders and praying mantises away also.

    Thanks again
    Kindest regards



    Hello Lindi

    I am sure you must be very upset about this. And there could be various reasons – but let’s explore some of them.

    Firstly, elsewhere (if you search on Hot Tags) you’ll see at various points where we’ve discussed that not every monarch egg is destined to become a butterfly. As well as the predators and parasites that we can see, there are viruses and diseases and pathogens that we can’t see – just like we can’t see infections like a cold and the flu virus.

    A monarch lays 300 or 500 or even a thousand eggs. Not every one will become a butterfly -0otherwise they’d become a pest. There are various predators, parasites and pathogens to keep the population in balance. That’s Nature. So 124/157 is not a bad average!

    It might be some consolation but that doesn’t help you, though. Of the various things that can kill monarch caterpillars, probably the worst is Oe, short for Ophryocystis elektroscirrha. There is also another NPV or Nuclear Polyhedrosis Virus.

    I won’t explain these any further here as it’s been discussed in many other posts, so I suggest you click on the Hot Tags to the right, e.g. “disease” and “pests”. And here are some other very useful sites to look at:

    I have a huge amount of respect for Edith who hosts the website, but remember that these sites have been written for an American audience. There are no true butterfly farmers here in New Zealand – all of us to some extent protect wild bred monarchs – and of course it is therefore hard to create a perfectly sterile way of raising them (not that we’d want to).

    From time to time some of my caterpillars don’t make it. I guess right now I probably have 300-400 monarchs in stages from eggs to pupae in my “butterfly house” (an old greenhouse where they’re protected from predators). From time to time I note that one or two have died from similar or differing symptoms. A bit like life and death with humans really – not all of us make it to 90 or even 80. However, if I went into the house and noticed a really strong smell, or more than 3-4 with the same symptoms, then I would consider cleaning out the house, sterilising it well, killing off all the stock I had (plants and creatures) and “starting again”. If it was this time of the year I would probably sterilise the empty house and containers and wait until next spring before I started again.

    Hope that helps.


Viewing 4 replies - 1 through 4 (of 4 total)

You must be logged in to reply to this topic.