Koolau Spur-winged Long-legged Fly

A fly that could not fly

The tiny Koolau spur-winged long-legged fly, measuring between 15 and 18 millimeters, had no wings and was therefore flightless. Instead of wings, it had spurs about one millimeter long. The reduction or loss of flight organs in animals can occur as an expression of certain ways of life, according to the Lexicon of Biology on Spektrum.de. This phenomenon can occur in very windy areas, for example on islands, coasts, in deserts or mountains. In insects, this reduces the risk of being blown out to sea in storms.

The extinct, wingless Koolau spur-winged long-legged fly was well adapted to life in strong winds. The insect was native to the Ko’olau Mountains in the Mount Tantalus area on the Hawaiian island of O’ahu and lived mainly in the forest leaf litter.

The Koolau spur-winged long-legged fly is one of twelve described species of Hawaiian long-legged flies that have no wings or only reduced wings. It is assigned to the genus Campsicnemus.

Koolau spur-winged long-legged fly – fact sheet

alternative name	Ko’olau spurwing long-legged fly
scientific names	Campsicnemus mirabilis, Emperoptera mirabilis
English name	Koolau Spur-winged Long-legged Fly
original range	Oahu (Hawaii)
time of extinction	1907 at the earliest
causes of extinction	big-headed ants introduced to the island, habitat loss
IUCN status	extinct

Big-headed ants – one of the worst invasive species

Not much remains of the Koolau spur-winged long-legged fly today—only three poorly preserved specimens collected in 1900 and 1907, now kept at the Bishop Museum on the Hawaiian island of O’ahu.

In general, research today assumes that the Koolau spur-winged long-legged fly was primarily wiped out by big-headed ants (Pheidole megacephala) introduced to the island in the 19th century.

Regardless of their actual origin (possibly southern Africa), big-headed ants are now found in many tropical and subtropical regions of the world. The Global Invasive Species Database (GISD) has even listed them among the world’s hundred worst invasive species. This is because the ant species is considered a serious threat to biodiversity, as it displaces native invertebrates.

In Hawaii’s lowlands, the big-headed ant has exterminated several insect species, including animals that were important for pollinating the local flora. The extinct long-legged fly species may include Emperoptera hardyi, E. hawaiiensis and E. zimmermanni. Among other things, the big-headed ant also caused the extinction of the tree snail species Achatinella buddii and Achatinella apexfulva from the island of O’ahu.

No one knows exactly when the Koolau spur-winged long-legged fly went extinct, but during a search expedition in the 1980s no animal of this species was seen anymore.

Not only the threat posed by big-headed ants, but habitat loss may also be responsible for the disappearance of the species, wrote insect researcher Neal L. Evenhuis in 1997 in Review of flightless Dolichopodidae (Diptera) in the Hawaiian Islands.

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