Giant Tenebrionid Beetle

The Giant Tenebrionid Beetle (Polposipus herculeanus) is one of the world’s most remarkable and endangered beetles. It has a highly restricted distribution, is only found on Fregate Island in the Seychelles, and is listed as Critically Endangered in the IUCN Red List of Threatened Animals.

Appearance

© Gideon Climo

This species is about 20-30 mm long, its colour is dark brown, it has long legs and a large rounded abdomen with raised tubercles. This beetle has defensive glands which produce a chemical secreted from the posterior of the beetle, which has a musky smell and stains the skin purple.

Lifespan

Its longevity in the wild is unknown, but two individuals, collected as adults of unknown age for an ex-situ breeding programme, survived over seven years in captivity, although the average age in captivity is approximately half of this.

Behaviour

The beetles are arboreal and nocturnal. They live on trees and decaying logs. They normally hide in crevices and under the bark of trees during the day, and come out at night to feed. The beetles like big trees with flaky bark, fissures, cracks and crevices as they provide refuge in which to hide from predators during the day. Being fairly large and flightless, they cannot travel very far, so they normally hang around the same spot. The furthest a beetle travelled was 19 m as reported in a recent study, but most of them were seen again and again on the same tree. They live in large groups and often cluster tightly together in crevices on branches or under bits of wood on the substrate.

Conservation status

Being endemic and having such a restricted distribution, the giant tenebrionid beetle is considered especially vulnerable to extinction from the events such as the introduction of disease or alien species, and from natural disasters. Nature Seychelles has been monitoring the beetle for several years and initiated research with Reading University on its ecology. One potential conservation measure is the translocation of the species to other islands in their considered formal range.