Wendy Day, of Mosgiel, asks :-

Every now and then, I have picked up from my hall carpet what at first looks like a piece of cotton or thread. It is brown and about 3cm long. When I get it in my hand it moves about. Looking closely it is like a very tiny caterpillar. I havn't found them anywhere else in the house. What are they?

Peter Johns, a retired entomologist at the Canterbury Museum, responded.

It is the introduced millipede Ophiulus pilosus. It is a very common species whose males go walkabout usually after periods of rain then warm weather.

Populations do increase if calcium compounds are leaching into the soil during the building of houses or concrete paths when there also a lot of damaged and rotting vegetation around. Some years ago this very thing happened in Christchurch and all the new houses were invaded.

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