...but I was unable to identify it. Many thanks to Detective Rob for taking up the challenge and to Leonie of Landcare Research who replied...
'Your enquiry has been passed on to me. The beetle you have photographed is called a Squeaking longhorn beetle, Hexatricha pulverulenta, a native beetle. Apparently they make a squeaking noise when held. The grubs live in dead wood of dying trees especially beech and pine.'
A Google search reveals that Longhorn beetles belong to the Order: Coleoptera, Family: Cerambycidae - a large family that includes over 180 species endemic to Aotearoa. Huhu beetles also belong to this family. One Google link was to T.E.R.R.A.I.N - Taranaki Educational Resource: Research, Analysis and Information Network - http://www.terrain.net.nz/friends-of-te-henui-group/local-insects/beetle-longhorn-2.html - a Taranaki community resource that is a wealth of information and GIS technology.
Whilst I'm on the subject, have you heard of the New Zealand Biodiversity Recording Network at http://www.nzbrn.org.nz/index.aspx? After registering you can then record observations for birds, plants, fungi, frogs, geckos, skink, butterflies, insects and mammals. What a fantastic way to create a snapshot of biodiversity in your area - and learn about our unique flora and fauna at the same time. Yeah, I know that there's not always time but I reckon it will be a great retirement hobby!!