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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
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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.
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