Wellington Tree Wētā

Hemideina crassidens — the Wellington tree wētā — is one of about 70 species of New Zealand wētā (the indigenous name for several Anostostomatidae cricket-relatives) and the species most New Zealanders are likely to actually encounter. Adults are 4-7 cm body length with stout brown bodies, large heads, and dramatically enlarged mandibles in males (used for combat with rival males). The species inhabits tree cavities — natural hollows in trees, holes excavated by other invertebrates, occasionally galleries the wētā have helped to enlarge — across native New Zealand forest from sea level to the mid-elevation tree line. The most behaviorally distinctive feature is the harem mating system: a single dominant male defends a tree-cavity gallery and gathers a 'harem' of 1-10 adult females within. The male defends the gallery from rival males through ritualized wrestling combat using his enlarged mandibles — opponents lock jaws and try to push each other out of the gallery entrance, with the loser typically retreating to find a different gallery. The arrangement is one of the only documented true harem polygyny systems among insects (most insect mating systems are non-territorial scramble competition or single-pair arrangements). Females in a harem feed on tree leaves and fruits at night, return to the gallery during the day, and copulate periodically with the resident male. The wētā is a flagship species of New Zealand's invertebrate biodiversity and a centerpiece of conservation education programs across the country. Like the giant wētāpunga (Deinacrida heteracantha), tree wētā populations have declined under introduced rat and stoat predation, but unlike the wētāpunga the tree wētā remains widespread across the New Zealand mainland.