HIDE & SEEK
In these winter months, no longer do we hear the song of cicadas during the day and the chirping of field crickets in the early evening in our gardens.
However, life continues in its various life stages for all the invertebrate species that we see in the warmer months.
On a sunny winter’s day, we suddenly may see butterflies flying around visiting flowers. How the sight of a monarch going from flower to flower lifts our spirits! And even more uplifting is when the now-uncommon native yellow admiral flits around our flowers.
Both these species overwinter as adults, and on warm sunny days they feed on nectar before the next cold spell arrives. The yellow admiral ( Vanessa itea) hides away in cracks and crevices, waiting for the warmer months to return to lay their eggs on nettles. Monarchs ( Danaus
plexippus) are the only butterfly in New Zealand that can congregate in large swarms for the winter. Sexually immature monarchs that emerge late in autumn survive over winter to start the next generation. These adults have a strong sense to congregate on suitable sheltered trees (to protect them from storms) near a supply of winter flowers with nectar.
We do not see the white butterfly over the winter months.
Pieris rapae overwinters in the pupal stage, not hatching until consistent warmer temperatures return.
Finding and removing chrysalises, then killing them humanely in a container in a freezer (as you can do for all pest species) seems an obvious choice to reduce the potential white butterfly population for the coming season.
Alas, it is not as simple as that. Many chrysalises may have already been parasitised by a small wasp. This beneficial wasp forms part of a suite of parasitoid species that can naturally control the numbers of this butterfly at different stages of its life cycle.
Adult tree wētā are always around, as are the young.
Hemideina thoracica are not often seen unless they move into a shed and hide in unexpected places. And no wonder – the urban environment is a bit of a jungle for tree wet¯a¯ compared to pre-human days. Now, they are not only eaten by birds, but also by introduced cats and rats. If not eaten, tree wet¯a¯ can live at least eight years.
The native praying mantis ( Orthodera novaezealandiae) usually overwinters in its egg case (ootheca).
The southern African mantis ( Miomantis caffra) does this too, and is now the mantis more commonly seen in Auckland gardens.
In July 1983, I unexpectedly discovered both adults and nymphs of the native mantis still present in my garden despite frosts. Over several months, most of these remained within a metre of their initial discovery site. They could be observed most days when the light was good. On several frosty mornings, three nymphs living on a golden conifer had the overnight dew frozen on their backs, which immobilised them. Later in the day, when it was warmer, however, they could follow my movements and move freely.
Up to then, cold temperatures were the accepted cause for the disappearance of mantises over the winter period.
The introduced Australian passion vine hopper lay their eggs in the compound umbel seedheads of fennel and the tendrils of grapes.
Some fennel stems look like they have small spines or teeth on them. These raised areas result from notches made by female passion vine hoppers; an egg is laid in each notch. Eggs hatch the following spring, so it is important to remove and dispose of vegetation containing these overwintering eggs to minimise hopper numbers in the following season. You can bury the removed vegetation or destroy it in some other way such as hot composting.
The passion vine hopper eggs may be parasitised by a tiny beneficial wasp, but these wasps do not hatch until late summer. For many gardeners, this is too late, as by then the new generation of passion vine hoppers would have reached adulthood and nearly completed their life cycle. This is a good example of synchronisation of life cycles of a wasp with its pest host that conflicts with the desires of gardeners!
And in the protected depths of soil and in compost heaps, unseen small invertebrates continue to grow and thrive during the colder winter months.
Some aerial species, like whitefly, apparently disappear for these months… to the delight of kale eaters who can now also enjoy the enhanced flavour of kale from it being frosted.