Category: Invertebrates

Mimopeus opaculus

I associate this large darkling beetle with predator-free offshore islands, yet Andrew Crowe in “Which New Zealand Insect” says it is common on the mainland south of Auckland.

It’s probably fair to say the animals on islands in Cook Strait and Marlborough are larger than normal though. Mimopeus opaculus is about 20 mm long and is common on Puangiangi, having survived rats and now apparently thriving. They congregate under cover in the daytime and feed at night, being seen on the ground and on tree trunks.

Of the 150 species of darkling beetles in New Zealand, there are several on the island and I have earlier posted some photos of the smaller Artystona rugiceps. Its common name, which I am not convinced is commonly used, refers to the grubs. Mealworms, used for feeding robins among other fun activities, are the grubs of Tenebrio molitor, which is in the same family.

The animal below has a very small passenger or parasite behind its right eye. The mite is under 0.5 mm long:

Artystona rugiceps

This flightless beetle is a bit under 10 mm long and is quite common on Puangiangi. It’s seen on tree trunks after dark, where it feeds on lichens. Ian Millar and John Marris (Lincoln University) placed it in Artystona, which is endemic to New Zealand.

The species designation is likely but not certain- it’s pretty difficult to get a full identification from a few photos. What’s important is getting an overall impression of the invertebrate fauna on the island and to see if that informs us about ecosystem health and whether it is typical of what we should see in the region.

These beetles are Tenebrionids or darkling beetles, named because they are nocturnal. All told there are about 150 species of darkling beetles in New Zealand. This is one of the smaller ones on Puangiangi. A. rugiceps is the species most frequently reported on iNaturalist and is found throughout the country.