NC State University Insect Museum

"ugly" mouse-sized "grasshopper" in the news

Feb 24 2009, 10:21:22 PM EST in category [insects] by ardeans

Wonderful image of a giant weta, captured by Laura Molles.

Poor giant weta.
New Zealand's devil insect?
I beg to differ.

While combing the Web for news-of-the-cool I ran into an article about the Cook Straight giant weta, Deinacrida rugosa Buller, 1871 (Orthoptera: Anostostomatidae) and its slow but hopeful resurgence in New Zealand. Several aspects of this story motivated me to report upon it here, but mainly I feel compelled to clear up two errors (one real, one subjective):

Weta are classified in Ensifera (crickets and katydids, which have long antennae, auditory organs on the prothorax, and 6-valved ovipositors), and are not really "grasshoppers," which belong in Ensifera's slightly larger sister, Caelifera (true grasshoppers and locusts, which have short antennae, abdominal tympana, and 4-valved ovipositors)
Weta are neither "ugly" nor "grotesque-looking"! Perhaps the title was a reference to the origin of this taxon's common name, which is a contraction of Wetapunga - the "god of ugly things" or "monsters of the night".

But also it feels good to highlight an important conservation effort focused on hexapods. These giants can weigh up to 40 or more grams and are among the most massive insects in the world. Weta evolved in the absence of rodents (and may actually play the roles of rodents) until about 800-2,000 years ago, when humans arrived in New Zealand and brought the Pacific rat (Rattus exulans) with them. Other predators followed, and soon giant weta were extirpated from the main islands of New Zealand. What made them vulnerable? Gibbs (1998) explains:

Their size alone renders them preferred targets (4-40 g).
They are flightless and totally apterous.
They have a strong olfactory presence. Although not investigated chemically, there is ample evidence that weta communicate with pheromones. They are distinctly "smelly" to the human senses.
All species are nocturnally active and relatively slow moving.
By day they retreat into a sheltered refuge which may vary from simply a leafy haven in the canopy to a gallery in timber or soil into which the weta squeezes itself either head first or rear first.
They may be solitary or distinctly gregarious.
An acoustic communication system is developed and is used also as part of a defense or threat display in some species in which the heavily spinose hind legs may be raised over the head and rapidly lowered.
The life cycle requires about 18-36 months for egg-adult development, depending on species and altitude; adults live for perhaps 9-30 months.
Oviposition is in soil or soft rotten wood.
They are perhaps best described as omnivorous scavengers but they range from species that are almost exclusively herbivorous to others that are exclusively predaceous.