A plague of monarchs

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  • #46165


    I’ve done this exercise before…

    Imagine a garden without monarch predators. If a pair of monarchs came to this garden on 1 September and the female started laying eggs…

    Scientific data tells us that a female monarch can lay 300, 500 or even over a thousand eggs. Let’s say she lays 500, of which half are females. So on or about 1 October these 250 females start laying and lay 250 x 250 = 62,500 eggs.

    This continues all season. It’s a perfect season for monarchs. None of them are going to get diseases, eaten or parasitised.

    1 December there are 15,625,000 eggs
    1 January 3,906,250,000 eggs
    1 February 97,656,300,000,000,000 eggs
    1 March 24,414,100,000,000,000,000 eggs

    That’s quite a few monarch butterflies flying around!

    In truth, some monarch caterpillars are destined to feed other species – even the soil. We’re fortunate that monarchs slot into our native ecosystem and don’t have any negative effect on our native plants or animal life. If there were a lot of wasps (as in previous years) the monarchs wouldn’t “control” the swan plant,and it could get listed as a pest plant, with the seed blowing into gardens, farmland and our native forest.

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  • #46735


    Hi Swivel… do you have ants on your plants? They might be taking the eggs. Try some ant poison at the base of the plant.



    Mmmm, I think in reality even if all “pests or preditors” were eliminated available food would dictate just how many Monarchs we would have. As time progresses it seems to me that it becomes more difficult each year for the new generation to establish, by that i mean that the over winterers start laying their eggs as soon as the weather allows but virtually none of them hatch. Why is this? I have no answer except to venture that it is not global warming. In each of the last 2 or 3 years I have become concerned that a new generation was not going to eventuate, this year, 2015 being the slowest, the first generation of only a few “cats” got through to begin laying in late December. (This is in Northland) now mid January 2016 there are hundreds of cats of all sizes and clearly there is going to be a feed shortage for their progeny to contend with.

    Since late October 2015 I have patrolled the swan plants several times a day in search of wasps and eliminated them, sometimes more than 50 in a session. Now, Jan 2016 I rarely see more than 4 or 5 in a 15 minute patrol. My cats to my knowledge are maturing in a paradise virtually free of preditors. In fact only in the last 2 weeks have I seen a wasp ( on 3 ocassions) devouring a cat,—-it’s last meal.

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