Are caterpillars safe from wasps now?

March 2026

There is a point where wasps swap their focus from taking protein, often in the form of caterpillars, to nectar and / or fruit, and the last pre-winter generation of monarchs have a far easier time growing to adulthood.

We know from Landcare Research work that for vespula wasps this will be during the second half of March when the drones and next season's queens emerge to mate. In DOC-funded research based in Northland, the vast majority of paper wasps caught in late March / early April had been collecting nectar.

So, are caterpillars safe to be left in the garden now in Auckland? It's a good question. It is definitely safer.

European and southern Australian paper wasps feeding from solidago

In my garden about two weeks ago there was a marked increase in the paper wasps taking nectar from the flowers, but I was still seeing hunting activity where the wasps were searching on leaves for caterpillars. This week I have only seen one paper wasp and one European tube wasp that seemed to be interested in something other than the nectar. The rest are fighting over the swan plant flowers. I've also seen a vespula wasp have a go at a monarch butterfly in order to get to tropical milkweed flowers. Indeed, be aware that the vespula wasps are likely to be at their most aggressive at the peak of the nest population.

Additionally I found a monarch caterpillar on one of the swan plants in the garden. It was still there, and a lot bigger, a few days later. However this is one caterpillar. It's acting as the canary in the coal mine. Given the number of eggs the monarch female must have laid, one caterpillar surviving to later instar stages is not a sign of safety in the garden. We have to remember that In a naturally balanced ecosystem, only 5-10% of monarch caterpillars would manage to reach adulthood, but that would still mean more than this one lonely larva.

Monarch-no-mates: The one and only surviving monarch caterpillar in the garden

However I think we are very close. I would not be surprised if we only need to wait another week before predation rates bottom out in Auckland and there is good reason to then leave the monarchs in the garden. Evidence from the United States shows wild monarchs have more stamina than those raised in captivity, and for the generation that needs to get through the winter here in New Zealand, even an Auckland winter, that difference will be important.

Southern Australian paper wasp feeding on tropical milkweed

I would love to hear what is happening in your gardens and whether you are seeing signs of caterpillars still being taken or whether they are now thriving.