Congregating butterflies

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  • #47251


    For the last week we have noticed monarch butterflies flying and landing in our gum trees. This afternoon there were more than ever. I counted up to 40 and then lost track. There may be up to 50. We have no swan plants and live in a semi-rural area near Rotorua. I am wondering why they are grouping in such numbers here. Do they migrate? Would they be resting? Or is there just something about our trees and location that attracts them?

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  • #47253


    Hello KK.

    This is a sign that winter is coming. Monarch butterflies meet up in large numbers to roost in favoured trees just like yours, top up their nectar reserves during the day, and then will either adopt that site as an overwintering site or migrate to a permanent overwintering site.

    When the late summer and early autumn monarchs emerge from their pupae (chrysalises) they are biologically and behaviourally different from those emerging in the summer. The shorter days and cooler air of late summer trigger changes. Even though these butterflies look like summer adults they won’t mate or lay eggs until the following spring. They are in ‘diapause’, i.e. sexually mature but don’t breed until the spring.

    It would be very helpful if you could monitor the trees, reporting in once or twice a week to and giving an estimate of the size of the cluster. We will be interested to hear how the monarch numbers build up or decline.

    It is thought that they are attracted to trees where they can leave behind pheromones to remind them in following years that that was their site.

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