Robust grasshopper

Status: Nationally Endangered

If Game of Thrones ever needs to cast a grasshopper in fantasy armour (available in either riverstone grey, black or orange), Brachaspis robustus is a shoo-in.” (North & South, 20 April 2019)

While the Robust grasshopper (Brachaspis robustus), is indeed a grasshopper, they don’t live in grass and they certainly don’t hop from blade to blade. Instead, these amazing little creatures inhabit riverbeds and terraces in the Mackenzie Basin. Highly threatened, it epitomises the vulnerability and beauty of these special habitats that have been disappearing fast (see threats). And while it can hop, it’s more like a leap of faith that ends in a crash-landinghence the armour plating.

Description

New Zealand’s largest lowland grasshopper, it’s cryptic (hard to see) amongst the stones and boulders of its specialised habitat, using camouflage as a defence against predators. Males (18-22mm) are much smaller than females (38-44mm). Like many NZ grasshoppers, they’re flightless (wings are around 1-2mm). Three colour morphs are known: ‘Grey’ (~60%), ‘Orange’ (~40%) and (<0.5%'Black'(<0.5%). It lives for ~ 2years. Eggs are laid from early summer to mid-autumn. Adult females probably lay two egg batches a season, each containing between 20–32 eggs. Most nymphs emerge in mid-summer, which seems to indicate the eggs require a winter period in order to develop fully. The nymphs then overwinter, often surviving temperatures well below 0°C, and reach adulthood the following summer.

It’s found only in the Tekapo, Pukaki and Ohau river catchments in the Mackenzie Basin, from Lake Benmore in the south to the upper Fork Stream in the north.

'Orange' variant. Photo: NZ Snowman @ Wikipedia
‘Orange’ variant. Photo: NZ Snowman @ Wikipedia
Female 'Grey' variant mating with the much smaller male. Photo: NZ Snowman @ Wikipedia
Female ‘Grey’ variant mating with the much smaller male. Photo: NZ Snowman @ Wikipedia

Conservation efforts

Two projects are currently underway in the MacKenzie basin, where a specially designed 500m perimeter fence was installed in partnership with Te Manahuna Aoraki to exclude hedgehogs, rodents, and mustelids

  1. The robust grasshopper project, which is assessing methods for species management and monitoring techniques. This project includes a University of Canterbury PhD thesis due for completion mid-2019
  2. An MSc project to identify whether robust grasshoppers increase in population size following exclusion of predators, due to be completed in 2020