January 2020 – Trove

Auckland Tree Weta

Hemideina thoracica

The tree weta is guaranteed to evoke a strong response in most people who encounter them. They have barbed legs, overlapping amourmed plates on their backs, fierce mandibles, ovipositers that resemble large stingers, and an ability to jump a considerable distance. When threatened they will throw their back legs over their heads in attempt to intimidate their foe by looking larger and spiky, and make a rasping noise by rubbing their legs against their abdomen. The males have a particularly fearsome visage, in the form of an over-sized head which resembles a horse’s, and will also hiss menacingly. In reality, they are mostly harmless, and can make an interesting if undomesticated pet if a weta box is provided as a residence.

Left to their own devices they live in holes in trees, called galleries. The holes are formed by moth or beetle larvae, or rotted off twigs. A gallery will consist of maybe ten weta, juveniles of mixed sex, females, and one male who rules the harem. The male with the largest head reigns supreme, and it takes three instars to reach maximum head size. Males with smaller heads can mate with females outside the harem, but can also mate with the females of a harem if the dominant males head becomes too large to fit into the gallery entrance!

They are nocturnal, and aboreal, as their name suggests. They feast on soft leaves as a preference, and small insects. They provide a tasty snack for many of our native birds, kiwi, robin, ruru, and tomtit, but are also predated on by the usual introduced predator suspects; rodents, mustelids, hedgehogs, and cats.

Silver brooch

Sand Scarab Beetle

Pericoptus truncatus

mumutawa/ngungutawa

The mumutawa beetle is a sturdy beetle, with an impervious looking carapace and torso, and chunky legs adapted for digging, and rowing through sand. It’s the largest of New Zealand’s native scarab beetles, and is found throughout coastal NZ, above the high tide mark, though it requires a lot of dampness to stop it dehydrating and dying. A nocturnal beetle, it emerges of an evening to fly and wander about in a blundering fashion, on the lookout for food and likely mating partners. The traces of their nocturnal ramblings can be observed in the sand trails they leave behind them.

The female beetle lays her eggs deep in the sand; larvae have been found living more than a meter underground, feasting on the roots of marram grass. They have a tendency to be parasited on by an exotic wasp in Northland, which stings, paralyses, and lays eggs in the hapless larvae. The eggs hatch, and the wasp larvae feast on the mumutawa larvae.

The beetle larvae have been seen perambulating down to the low tide mark at night to cover themselves in salt water. It is posited that this may kill some parasitic mites.

The Pericoptus truncatus was the first beetle collected in New Zealand by Joseph Banks in 1769.

Silver brooch

Little Blue Penguin

Eudyptula minor

Korora

There are 18 species of penguin worldwide, and 9 of them breed in New Zealand territory. The korora is the smallest of that unique species, 30cm high, and the only flightless seabird you are likely to see in the Hauraki Gulf.

They spend their days out at sea in search of small fish, squid, and octopus, coming ashore at night in convivial little groups called ‘rafts’, to roost.

On Rakino Island, some fortunate residents have korora nesting under their baches, or sheds, though they may debate the description ‘fortunate’ when they are kept awake at night listening to the squabbling of little penguins!

Little blues come ashore between January and March and must spend two weeks moulting, replacing all their feathers before they can head out to sea again. They are very vulnerable at this time to dogs, so this is a good time to ensure our dogs are on-leash in known penguin areas.

If you see a listless, scruffy little penguin at this time, just give them a wide berth, and leave them to get on with moulting.

The biggest threat to korora on land are introduced mammalian predators; rats, mustelids, feral cats, and dogs. Happily Rakino is predator free, so to keep the korora safe, we only have to ensure that cars drive slowly and carefully at night, when penguins may be on the roads, and that our island dogs are under control, and leashed when penguins might be in the vicinity.

Eyrewell Beetle

Holcaspis Brevicula

Status; extinct

Only ten Eyrewell beetles have ever been found. No more will be found, as their habitat of kanuka and exotic pine trees has been replaced by 14,000 cows, at the behest of Ngai Tahu, in a dairy conversion that happened in 2019. DoC attempted to work with the owners of the land to ensure some protections for the small black carabid beetle, but were ignored. Unfortunately our conservation laws do not extend to private property, unless the endangered flora or fauna at risk is protected under the Wildlife Act.

The Eyrewell beetle was threatened from the outset, when it’s kanuka habitat was destroyed to make way for exotic pine plantations, the eponymous Eyrewell Forest. It survived on to exist in 7000 hectares of pine, but when the pine forest was returned to Ngai Tahu in 2000, the beginning of the beetles’ obituary was written.

Small, black, flightless, and un-charismatic, the beetle had no chance of prevailing when pitted against the prospect of income generated from the sale of milk powder and infant formula, grown off the back of a center pivot irrigation system, fed by the Waimakariri River, in a traditionally dry region of Canterbury.

The Eyrewell beetle was about 1 cm long, shiny black, nocturnal, and couldn’t fly, though it could run, but not fast enough to outrun the shredders that chipped the pine trees up into sawdust so fine any creature larger than a pinhead could not survive. It’s tenacity that ensured survival of it’s earlier habitat destruction could not survive this final blow.

Silver brooch