Hemideina thoracica (White, 1842)

REDUCED_NZ-Ento-Soc-Insect-Playing-Cards_Tree-Weta REDCommon name: Auckland tree wētā, tokoriro

Order: Orthoptera        Family: Anostostomatidae

Size: approx. 40mm long

The Auckland tree wētā is one of seven tree wētā species in New Zealand. It is found over much of the North Island, other than in the Wellington region where another tree weta, H. crassidens, is found. Tree weta live in galleries inside trees, which they access through holes that are formed by a twig falling off or created by other insects such as pūriri caterpillars. At night wētā come out of their tree holes to nibble on the leaves, fruits, and seeds of neighbouring trees, such as mahoe (Melicytus ramiflorus), and will also scavenge on other dead invertebrates.

Wētā are a popular food item for many of New Zealand’s native birds, so hiding in tree holes when not out feeding helps to avoid predation. If threatened, wētā raise their spiny hind legs in a defence display, to try and scare away the approaching predator. They can also make a scratching noise, called stridulation, by rubbing little pegs on their legs over their abdomen. They stridulate when disturbed, but also make these noises during mating and during aggressive interactions with other males. Wētā have tiny ears on their forelegs which allow them to hear these scratching sounds.

Inside the tree holes, wētā often live in groups made up of multiple juveniles and females, with just one or two males. Males defend these ‘harems’ from other males using their large heads and mandibles (jaws) as weapons during fights. Head size is highly sexually dimorphic, meaning males have bigger heads than females, but overall body size tends to be larger in females. Having the biggest head allows males to win fights and secure galleries with more females.


Resources:

Trewick SA., Johns PM., Fitness J., Morgan-Richards M. (2014). Weta Geta – an online guide to New Zealand Orthoptera. Retreived from http://www.Wetageta.massey.ac.nz on November 2016. Last updated June 2015.