Pteromalus puparum

This topic contains 13 replies, has 6 voices, and was last updated by  hayleypearl 5 years, 4 months ago.

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  • #14741

    NormTwigge
    Keymaster

    Hi Anna,

    The Pteromalus wasps depicted in the photo you posted are not attacking the pupa, it has already been infected at an earlier stage and the wasps are emerging from it through a small hole in the pupa. You must remove the pupa and destroy it quickly, as 100 plus wasps can emerge. The wasp infects the caterpillar at the stage of hanging in a ‘J’ and as soon as the caterpillar sheds its skin the wasp will inject its ovipositer into the soft pupa and deposit anything up to 150 eggs inside.

    These hatch into grubs which then devour the contents of the pupa and then themselves pupate inside the host. The first adult chews a hole in the casing of the host pupa through which most of the following adults will emerge, mate immediately and then search for fresh pupae to infect. Once the pupal skin of the host has hardened the wasps are no longer interested in it. Pupae gathered from outside in the garden can be already infected, or one single female wasp can gain access to the butterfly house either by hitching a ride on clothing, simply by flying in when someone enters the butterfly house, or as in the castle of a castle as well – by hiding on the underside of a potted plant leaf when it is introduced. They can gain access through an extremely minute gap, but probably not the fine mesh on a castle. These wasps are destructive little demons and can wipe out a generation of admirals in a butterfly house in a very short time.

    The safeguard is to place the admiral larvae that are of pupating size into the likes of a castle that will exclude entry of any of the critters, and allow the larvae to complete the pupation phase in safety.

    They will also infect monarch caterpillars, but not to the same degree, and have no problem finding their way through most of the shade cloths and standard sreen mesh.

    Unfortunately you are experiencing what most breeders contend with at some stage, and will be able to take measures to prevent it. Keep an eye on any hanging ‘J’ caterpillars for signs of the wasp, for they will patiently wait up to 2 days near the hanging caterpillar, or sometimes even on it, and are ready to do their deed when the skin is shed. Occasionally an admiral pupa will violently shake and swing when touched or disturbed, and it is a defensive move to try and shake off the likes of a wasp, usually to no avail though.

Viewing 13 replies - 1 through 13 (of 13 total)
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  • #36815

    hayleypearl
    Participant

    Ahh I see, thanks Norm. I will keep an eye out for next time. Unfortunately this caterpillar didn’t make it. It was pupating but only got about 1/3 of the way before it stopped and I believe it is dead now as it has not moved since. Not sure if the wasps had anything to do with that but is the first time it has happened. I’m relatively new to this.

    #36812

    NormTwigge
    Keymaster

    hayleypearl – The wasp does not infect the caterpillar hanging in the “J” position but will wait patiently until the caterpillar sheds its skin to pupate. At this stage when the pupal skin is still soft and before it hardens, the wasp will insert its ovipositor into the pupa and deposit it’s eggs. They are determined little beasts and the one you swatted away, or others, may well have been close by waiting to strike at the right moment.

    #36803

    hayleypearl
    Participant

    I saw one of these on my caterpillars hanging in a J-shape yesterday…I swatted the wasp away and tried to kill it. We have a issue with wasps here, but I didn’t realise it was a wasp at the time. Does this mean the caterpillar is likely to be infested now?

    #36800

    mhm_dabbagh
    Participant

    Hi
    I want to know some question about Pteromalus puparum
    Would you please help me to find some reletive information about:
    1- Generation type
    2- The number of that Generation
    3- Life table of Pteromalus puparum
    4- Sex ration of Pteromalus puparum
    Sincerly
    Mohamad

    #26885

    Anna
    Participant

    With the Magpie Moths Norn, I have released most, but kept two pairs in the caterpillar castle, as they were mating, so I have put plant in there for them to deposit eggs on before I’ll let them out.

    #26884

    Anna
    Participant

    Thanks Norm. I noticed the caterpillar looking strange so isolated it (It was one I found on nettles in the vege garden) The caterpillar looked hunched up, and very short for its size…then I noticed the ‘dangler’ and coccoon.

    #26880

    NormTwigge
    Keymaster

    Hi Anna,

    Great to hear you are including magpie moths in your rearing. Your mention of the wasp whose cocoon hangs from a thread is Meteorus pulchricornis, a wasp accidentally introduced into NZ in 1996 and appears to be spreading quite rapidly. The wasp parasites the caterpillar, and when ready to pupate the grub emerges through the skin of the caterpillar, which then dies.
    From cropping areas, where it parasites pest caterpillars, there are concerns that it may move on to native lepidoptera, and has already been reported infecting kowhai moth larvae and admiral larvae.

    #26879

    Anna
    Participant

    Thanks Jacqui. We arrived home tonight after two days away to be greeted by 15 magpie moths, lots of monarchs and several Yellow Admirals all safely emerged from their pupae, so I’ll release them in the morning.

    #26877

    Anna
    Participant

    I forgot to add, that the beauty of having several “Castles” and containers is that I can isolate pupae, or caterpillars found in the garden from the ones that have been protected from the ovum stage, just incase.
    I find ‘butter muslin’ from a fabric shop makes a great cover to use for protection caterpillars/pupae in a couple of plastic goldfish bowls too, as its close weaved, but breathe-able.

    #26876

    Jacqui
    Keymaster

    Good on you, Anna! You sure are doing your bit!!

    #26875

    Anna
    Participant

    Thanks very much for that Norm.
    I agree that it is a real uphill battle for the poor Admiral Butterflies!
    This one in the photo was one escapee caterpillar, that had just formed its pupae, and was still wriggling when I saw it. As soon as I had taken the photo I destroyed it, along with all the tiny wasps that I could.
    I had already had a run in with this wasp several weeks ago when I heard a pupae “knocking’ furiously in its container, and on closer inspection noticed a tiny insect on it, so I isolated it in a petrie dish, and some days later, the tiny insects emerged, and so I have kept them along with the pupae with the hole in it, still in the dish to show people.

    I also have one of those wasps that infect a caterpillar, then the coccoon hangs down from a thread till the wasp hatches…in my collection of “baddies”.(Safely in a sealed petrie dish)
    All great for informing anyone who shows an interest.
    I have learnt a lot about these from this forum, and it has helped me have more of an idea as to what they are.

    Luckily for the Admirals I have at least 100 pupae at the moment, safely in a caterpillar castle, with lots more caterpillars in another, and they should be safe till they emerge, and are released.

    …and I should add, I keep an eagle eye out for any parasite that may dare to come near them!

    #26874

    NormTwigge
    Keymaster

    Hi Anna,

    After looking again at an enlargement of your photo my first comment is probably not correct. What I picked to be an exit hole in the pupa may just be a mark on the surface, and if the pupa was fresh thay are indeed infecting it, which makes it important to dispose of it. I must admit I have never seen so many wasps on one pupa in all my years of breeding, usually one or two is normal, so it indicates some freshly emerged wasps near you. The above lengthy post was mainly intended for others not familier with the wasp, and what to look out for. I have dissected infected admiral pupae and counted up to 160 Pteromalus grubs in one pupa,so the poor admirals are having an uphill battle.

    #26873

    Darren
    Participant
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