nigelrc

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  • in reply to: Gum tree caterpillars #58567

    nigelrc
    Participant

    I last reared this interesting species (Gum Emperor Moth) as a kid in Tawa, north of Wellington. (I’m now 76!). At that time, the main population was around Whanganui, but it clearly spread gradually, as I’ve seen the cocoons on a pepper tree just out of Hamilton, & on a gum tree south of Auckland. Despite looking on gum trees in places (in Auckland) where there used to be populations, I’ve not succeeded in finding any evidence of them in recent years.

    Can anyone throw more light on the reasons for the apparent decline in the population? It would seem an unnecessarily hysterical reaction if biological controls have been introduced to protect eucalyptus plantations as the moths do not fly far & are unlikely to be present in such large numbers that the larvae became a severe pest. Is there more specific information about how any biological control works & is spread?

    As far as the life cycle goes, my experience was that eggs are laid around Nov/Dec, & the larva feed during the summer, pupating Feb/Mar. The moths emerge Oct/Nov. I had not known of them taking more than 8 or 9 months to mature in the cocoon.

    I’d be most interested to know if or where any populations continue to exist…

    in reply to: Monarch Population Survey Dec 2019/Jan 2020 #57955

    nigelrc
    Participant

    Here in central Whangarei, exactly the same early summer pattern as last year…butterflies seen in the garden virtually every day, & eggs regularly laid but then they disappear & hardly any larvae observed. I got worried about this previously but calmed down when the breeding season took off in the autumn as wasps disappeared & continued all through winter. Only the cold wet weather in August caused a blip. So overall, the monarch population continues to look healthy. It’s by far the most commonly observed species in my garden during the year as a whole.

    in reply to: Admirals in Northland #57883

    nigelrc
    Participant

    Is the White Admiral release area confidential information or can anyone visit to observe? What is the chronology of the life cycle? You would hope that co-ordination between the initiators of the project & the local council & roading contractors would avoid any damage or setbacks…

    in reply to: Admirals in Northland #57835

    nigelrc
    Participant

    Good to have the bigger picture & general advice from Norm Twigge. I see the odd Yellow Admiral butterfly in my garden between spring & autumn but have not consistently had them breeding on my Urtica dioica – & I’ve never seen a Red Admiral locally. Yellow Admirals did breed continuously on patches of nettles (U. dioica) in a relative’s garden near Russell & in one or two years the mid winter population of caterpillars was so numerous that they nearly stripped all the foodplants. The timing of the breeding cycle might be important – I guess a good population of caterpillars will have fewer parasites to contend with in winter…? I plan to try planting some Urtica ferox in suitable spots in a patch of covenanted native bush owned by relatives on the outskirts of Whangarei. I’m also encouraged to try & protect or cover at least some larvae if / when I next see them appear on my home-grown nettles.

    One further point of interest… Last autumn I observed what looked to be a freshly hatched Yellow Admiral settling on a patch of baby’s tears (Soleirolia) of which I have plenty in shady patches of the garden. The imago looked as though it was laying, but on close inspection I could find no sign of eggs. Although the plant is a member of the nettle family, I’m not aware that Admirals are able to breed successfully on it.

    Any update on the success of the Honshu White Admiral project in the Waikato?

    in reply to: Admirals in Northland #57828

    nigelrc
    Participant

    Good to get this input. Seems as if availability of preferred foodplants as well as predation by parasitic flies might be the determining factors in the success or otherwise of the Admiral population in Northland, NZ. It’s true that nettles of almost any type seem almost non-existent in this part of the country.

    in reply to: Admirals in Northland #57799

    nigelrc
    Participant

    Thanks for your useful observations & information, Elizabeth. I suspect one of the reasons for the scarcity of Red Admirals in Northland is that the native bush nettle (Urtica ferox), does not generally thrive in our humid climate, & is in fact rather rare in this part of the country. The Red Admiral appears to require this species to successfully sustain its population. Like you, I have attempted to grow this nettle in one Northland garden but it was very prone to slug & snail damage & proved difficult to sustain, particularly through dry spells. Before it succumbed, it did, even as quite small plants, attract one or two Red Admirals.

    But I think there is another significant problem that also affects the Yellow Admiral, & that is predation by probably more than one variety of parasitic wasp or fly. I had a large crop of Yellow Admiral caterpillars on my European nettles in early summer 2018 but was disappointed to note that very few seemed to survive to butterfly stage. I even found one or two chrysalids which never hatched & on close inspection observed a tiny hole where a parasitic fly had presumably emerged. I doubt whether there is much if any research into parasitic predation of native lepidoptera species so we are reliant on the careful observation of interested amateurs. It seems likely that this sort of predation might also be affecting the Forest Ringlet. We can only hope that the Research Project will throw further light on the problem.

    Sadly,it is not a realistic possibility for someone with a small town garden to prevent predation by protecting foodplants, at least on any significant scale…and even covering plants with gauze or mesh will not necessarily exclude small varieties of parasitic wasps or flies. I hope that some ideas might emerge about how to combat what appears to be a destructive imbalance in the predation of our native lepidoptera.

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