P. brassicae crysalides turn red before dying

  • Hello everybody.

    I have been trying to rear P. brassicae butterflies for some laboratory purposes. Using handpairing techniques I have managed to obtain already the second generation of larvae that are starting to pupate. Unfortunately the survival rate (for all the larval stages) is not great and some of the crysalides are starting to turn bright red before dying shortly after formation. Could this be some kind of virus or something? Or there could be some other factors impacting it? For example I have been experimenting with different foodsources and found out that the larvae fed with inner cabbage head leaves (white ones) are turning yellowish and getting more apatic until they die (but this was explained with the chemical changes within the cabbage as it varies by the leaf layers). All the food i have been given to them have been either grown personally or from known people therefore definitely free of any pesticides or insecticides.

    As the butterflies are adapting from wild, could it be that the biological clock is playing some tricks and they are dying because in nature they should not be active anymore?

    I would be happy for any suggestions for directions to look or find information or course of action.

    Thanks/ Danke


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  • Dear Kristine,

    I am pretty sure that the observations you reported here are due to an infection, most probably a viral one. You wrote that (most of?) the caterpillars already died before pupation. Did they shed liquid feces? I strongly assume that the cabbage parts you used for feeding contained too much humidity, leading to or supporting intestinal germs which finally kill the caterpillars.


  • Lepidopterix,

    thank You for the response.

    The condition of feces varied based on the food given, but they do hold together nicely. Some truly liquid ones were observed when Chinese cabbage was given as a food-source, so I disregarded it.

    Right now I'm feeding them with some soft leave (summer varieties) cabbage leaves. As the leaves are thinner than average cabbage leaves then it could be that they contain more water than cabbage varieties grown on field, made for winter storage. But this variety was growing faster and easier to obtain large biomass. I will try switching to hard leaved variaties (they are in growing process) as soon as they reach some feeding stage. Could the humidity in the rearing container play a role as well? Also that is the tricky part to balance the humidity so the leaves and the larvae does no dry out.

    For now I have got my hands on several book about insect viruses, but for now I don't know on where to begin the reading . In case of infection will disinfection with ethanol be enough or should i switch to other cleaning agents?



  • Could it be that the caterpillares had parasites? I read that may Butterfly species like Aglais io f.E. are forced by parasites. I lost 50% of my population of Aglias io as pupae because of parasites. (Pupae look different got black spots than died) I m´watched it on Atropos Pupase too. some black dots on the pupae, but none of the Atropos pupae died. So I guesses that the spots could be an infection. I ask an Entomologist, a friend of mine and he told me that so many caterpillars are parasited. That maybe depends on the Footplants too.

    maybe you find out something about how to fight parasites too.

    I hope the most of your pupae will survive!

  • Right now I'm tend to think that some of the larvae were infected with baculovirus, because of hanging or slow liquification. As the oldest larval batches are the more problematic ones, could it be that the virus kills them in the pupapal state or they are two separate problems...

    For now the fresher batches are ok, and there is one that should start to pupate soon (with a good larval survival rate), I guess I have to wait to see what happens in the pupal state.

  • That may be. There could be more than one or two reasons. I have that problem with Atropos caterpillars too. I did everything for desinfection and cleaning with several cleaning agents like kolloidal silver, sodium laureth sulfate, ethyl alcohol and even sterillium to clean the tanks, after that I had tham in the dishwasher...

    we will have to wait and see.

    Hopefully we will have Luck and all will be good and you will have many healthy pupae:daumenja:

  • Could the humidity in the rearing container play a role as well? Also that is the tricky part to balance the humidity so the leaves and the larvae does no dry out.


    according to my ample experience with rearing procedures, it is really vital to avoid too much humidity in breeding containers. Larvae are normally not impaired by too low humidity, but if humidity is fairly high, you may provoke the development of a plethora of ugly germs which infest your 'babies'. And, most important, always refrain from offering wet foodplants! You can not compare an artificial breeding situation with natural conditions like rain!!!

    Regarding your question on disinfectants: ethanol may kill a lot of germs, however, 'naked' viruses (i.e., such without an envelope), are resistant to ethanol. These nasty comrads can only be killed by heat, or strong bases.

  • DDeineDid you put your Tanks into the dishwasher? I do that now I read tgat helps a lot to kill germs. Virus can be kilked by kolloidal Silver 50 ppm. But it must be used careful it could harm the caterpillars. But what is interesting is that after I used the silver 2 caterpillars started to eat normal again and now they lokk healthy. I think the combi of dishwasher heat and silver helped a lot.

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