Jennifer Williams, of Green Bay in Auckland, asks :-
I found an unusual slug in the grass verge of my vegie garden which doesn't get any sprays. It was about five cm long, about 1cm wide, quite flat and was black with a cobalt blue stripe down one side. The site is 20 metres above the sea and well away from the native bush line. What sort of slug could this be?
Ruud Kleinpaste, an entomologist and TV's bugman, responded.
The slug you found is likely to be a "flatworm" (a Platyhelminth, belonging to the Class Turbellaria).
A flat worm stretches and contracts as it moves through litter layers and the soil. It also produces a good amount of slime - just like the slugs and snails.
Flatworms are carnivores. Their favourite prey appears to be earthworms, which they tend to envelop with their flat body. They them excrete some mucus, which slowly dissolves the earthworm's body and that allows the flatworm to literally suck up the dissolved, fluid earthworm "smoothy". Our native flatworm species are not well studied and certainly not well described, as far as I can determine. One thing is for sure, judging from my observations, our species come in spectacular colours and patterns, from purple blue and orange to rusty brown, pink, green and yellow-ish, often with stripes and blotches that wouldn't go amiss at a nineteen-eighties pop concert!
Of course, one of our native species famously breached quarantine in Ireland and became established there; it is now gobbling up Irish earthworms and causing quite some imbalance there in the pastures!