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Amychus manawatawhi

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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.

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Prodontria lewisii

Critically endangered, this small, flightless, unremarkable, brown beetle has a habitat of 81 hectares in the arid Cromwell basin of Central Otago. It was never a habitat larger than 500 hectares, and the construction of the Clyde Dam and resulting Lake Dunstan combined with land repurposed for housing development and a golf course has eaten up more than 80% of their original habitat.

The remaining habitat is under threat from the ravages of the Australian Redback spider, an unwanted import who makes it’s home in the abandoned rabbit burrows that litter the sandy loam the chafer beetle lives in. The Redbacks build a web in the empty holes, and repurpose them as a nursery for baby red-back spiders. Apparently one enterprising Redback had preyed upon 70 chafer beetles, as evidenced by the midden of crispy beetle husks piled in his lair. Chafer beetles are the second favourite prey of the Redback, after the darkling beetle.

Department of Conservation staff have been gingerly removing Redbacks from the former burrows with long-handled tongs, and then infilling the holes. This seems to be an effective solution for dealing with the spider problem.

Every December a chafer beetle larvae count is carried out by DoC staff, under the brutal Central Otago sun. More than 600 soil cores are removed from the earth, and hand-sifted through by the participants, in the hope of finding the elusive little grubs. The numbers found are generally very low, maybe just a few individuals. The beetle population is estimated to be about 3000. Cromwell chafer beetle larvae spend many months buried in the sand chewing through tussock roots. They go through three phases of instar before pupating for three months. When the adult beetle finally metamorphoses, it spends it’s days burrowed up to half a metre underground, before emerging on spring and summer evenings to mate, and feast on scabweed.

I don’t know if the Cromwell chafer beetle will survive all the threats it faces. It’s difficult to feel hopeful.

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Geodorcus ithaginis

A sea stack in the Mokohinau Islands known only as ‘Stack H’ may or may not be the last remaining home for our rarest beetle. Their habitat is the size of a generous living room; they have been predated out of existence everywhere else. They are so extraordinarily rare that their home can’t be revealed as unscrupulous poachers and collecters of endangered and precious creatures could feel compelled to liberate these beetles from their remote sea stack.

They are a good-sized beetle, the males up to 32mm long, the females slightly smaller, pleasingly stocky, flightless, and a slow perambulator, which is fortunate, because there is nowhere much for them to go on Stack H. The males have a protruding mandible used for battling other males for beetle supremacy.

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Stag beetles are under threat worldwide, mainly because of habitat loss. It takes a long time to become a stag beetle; they live as larvae underground for years before briefly becoming a beetle, and require a stable habitat of rotting logs and leaf litter in order to ensure their survival. The Mokohinau stag beetles do not have the luxury of leaf litter on their stack. They live amongst the peat-like substance that forms beneath the New Zealand ice plant, in tussock plants, and under rocks. Only rugged, sea-battered pohutukawa provide fallen leaves for beetles on Stack H.

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At the start I mentioned that Stack H may not be the last remaining home for the Mokohinau stag beetle… this is not because they may have another as yet undiscovered home. Unfortunately a recent attempt at a stocktake of the beetle numbers was an abject failure. Not a single beetle was located, despite repeated fruitless searches. Quite simply, there was no evidence of the beetle to be found. There is a slim possibility that there are some as yet unmetamorphosed larvae underground, and something has befallen the adult population, but more likely they have disappeared forever, another victim of habitat loss and predation by introduced species.

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