Every decade or two we have plagues of crickets, millipedes, and other small creatures, but this is the first time that anyone can remember such an abundance of these white butterflies.

This damper and cooler summer has clearly suited them. Perhaps the same conditions have disadvantaged their usual predators, particularly small wasps that parasitise the caterpillars.

It is only the caterpillars, not the butterflies themselves, that are a nuisance in the garden.

The caterpillars feed on brassica plants, such as cabbage, cauliflower, broccoli and turnip.

They do not eat tomato, zucchini or lettuce.

READ LAST WEEK'S NATURE NOTES RIGHT HERE: Who are these 'fun guys' that are appearing across the city?

The butterfly's main food is nectar from flowers.

Officially called the cabbage white, this butterfly is native to Europe, not Australia. Males can be identified from females by having one black spot on the front wing, with females having two.

The eggs are yellowish, and the caterpillars are green and fleshy, growing to about 25 mm.

There are several generations of cabbage white butterflies from spring through until late autumn. We rarely see them after late May. They survive the winter as pupae, resting (not feeding) over winter.