New Zealand is a bitter example of the havoc men can bring upon nature. By purposely or accidentally introducing a legion of alien species to this far-off land, men unleashed destruction and forever altered New Zealand’s unique ecosystems and indigenous wildlife. Rats, stoats, weasels, ferrets, feral cats and brushtail possums are the most notorious culprits because they predate on native and endemic ground-nesting birds like the iconic kakapo, kiwi and takahe, and many other less known species like the fairy prion and sooty shearwater, two burrowing seabirds. Introduced predators have driven several bird species to extinction in the past and continue to severely impact bird populations today.
The problem is not limited to the bird realm. The insect world is also in trouble as introduced bugs deplete native populations by killing or out-competing them for food. Non-native wasps are a notorious example: every year, they destroy large numbers of native bugs including bees, spiders, flies and caterpillars like those of monarch butterflies. Wasps are so numerous they threaten birds as well—here is an insightful documentary about the wasp plague in New Zealand.
More insidious, but no less detrimental, is the case of praying mantis.
A single praying mantis species, the endemic Orthodera novaezealandiae, was originally present in New Zealand. Another, Miomantis caffra or “springbok mantis”, was accidentally introduced in New Zealand from South Africa sometimes during the past century. First sighted in Auckland in the late 1970’s, the insect has been unfriendly to its kiwi cousin ever since.
Both species compete for similar habitats and therefore have overlapping ranges. Studies of interactions between the two species have returned astonishing results: native males are more drawn to springbok females than females of their own kind. This purely chemical attraction marked the demise of the New Zealand mantis in parts of its historic range, especially in the North Island, and the species continues to be displaced.
Like the European praying mantis—but unlike the New Zealand mantis—springbok females are cannibalistic and have the gruesome habit to devour males during or immediately after copulation. This behavior especially occurs when the female is hungry, so males have developed mechanisms to determine how well-fed is the female they court.
In the present case, mating does not occur at all: native males are merely killed when they attempt to mate with South African females.
In the South Island, praying mantis are a common sight but finding native specimens is a challenge. I have seen my fair share of praying mantis during the four months I lived in Nelson and none of them were native. In fact, I suspect that the very large garden where I repeatedly saw these insects has been entirely conquered by the springbok mantis.
Here are some photos of a springbok female from Nelson. Note its thin, long thorax—the section that starts behind the head.
Now, here is a young springbok specimen. Note the brown color.
The New Zealand mantis looks different from those. Unlike the springbok mantis, its body color is always green and it has a broad, flat thorax and distinctive blue and purple round patches on the forelegs.
Eggs also differ in appearance—this is what springbok mantis eggs look like:
I will continue to search for the New Zealand mantis, this time in Dunedin where I am more hopeful to find one as wildlife is particularly luxuriant in and around the city.
This springbok mantis was real keen to have a lengthy grooming session on the palm of my hand!