eTawau > Insects of Borneo > Flies > A stalk-eyed fly at Bukit Gemok

A fly with its eyes on stalks

A stalk-eyed fly on a dead leaf beside the George Mais Trail at Bukit Gemok, on a hot, bright morning in July 2015

At first it looks like any small dark fly resting on a dead leaf. Then you notice the head. Instead of sitting on the face, the two red eyes are carried out to the sides on long thin stalks, like a pair of pins stuck into a cork. It stayed for a few seconds, long enough for three photographs, then flew off and was gone. Looking for it again in the bright sunlight turned up nothing.

A small black fly with red eyes on long sideways stalks, standing on a dead reddish-brown leaf that lies across a large green leaf. Its wings, folded over its back, are dark with white patches, and its legs are long and orange-brown.
This is what you would see. The George Mais Trail, Bukit Gemok, 13 July 2015, 9.25 in the morning. The camera's flash has made the shaded background dark; it was a hot, sunny day.

What it is

A close view of the same fly from the side, with five labels: a red eye at the end of a long stalk; the eye stalk; short, sharp spines on the thorax; the dark-banded wing with white patches; and the thick front thigh.
The same fly, closer. Cropped from the first photograph and labelled; nothing else altered.

This is a stalk-eyed fly, family Diopsidae. It is a true fly: it has only one pair of wings. Several things together mark the family:

Few flies anywhere look like it. Some other flies have broad heads with the eyes set wide apart, but the diopsids are the family in which long, thin stalks with the eyes at the very end are the rule.

How far the name goes. The family is safe. The genus is probably Teleopsis, the commonest stalk-eyed flies in Borneo, many of which have banded wings like these — but that is a likelihood, not a determination, and the species are separated on details of the wing pattern, the spines and the eye span that three photographs from the side do not settle. The record has been posted to iNaturalist at family level, where specialists can take it further.

What the stalks are for

In many stalk-eyed flies the males have much wider eye stalks than the females, and the width matters. Two males facing each other line up their heads and compare eye spans, and the one with the narrower span usually backs down without a fight. Females, for their part, prefer to roost and mate with wide-eyed males. Some of the best-known studies of this were made on stalk-eyed flies from Malaysia. Whether this one is a male or a female cannot be told from these photographs: in some species both sexes have long stalks.

Stalk-eyed flies usually live close to water, in damp, shaded forest. They gather at dusk in small groups on hanging roots and threads over streams to spend the night, and their larvae feed in rotting plant material. Seeing one on a hot, dry morning on a hill trail, alone and quick to leave, is a reminder that the forest on Bukit Gemok is still damp and shaded enough underneath to hold them.

How big — not measured

There was nothing in the frame to give a scale, and it flew before anything could be put beside it, so this record has no size. Stalk-eyed flies are small: most are well under a centimetre long, eye stalks included.

Photograph and leave. Stalk-eyed flies are harmless. This one was photographed where it landed and flew off on its own.

The record

13 July 2015 · 9.25 to 9.26 am · a hot, sunny day

On a dead leaf lying across a green leaf, beside the trail

The George Mais Trail, Bukit Gemok, Tawau, Sabah, 12 km from Tawau, measured from the 0 km Tawau landmark. One fly, not measured, standing on a dead brown leaf that had fallen onto the leaf of an unidentified plant. Red eyes on long stalks; black, shiny, spiny thorax; dark-banded wings with white patches; orange-brown legs with thickened front thighs. Diptera: Diopsidae — a stalk-eyed fly. Genus and species not determined. Alone. It stayed a few seconds and flew off. Three frames, at 9:25:50, 9:25:54 and 9:26:33.
— iNaturalist observation 404467851

The same morning

Thirty-four minutes later, on the same hill, the same camera photographed a thickset, spiny stick insect holding its tail up over its back. Both records were at first read as night-time finds, because the camera's clock had been set to pm instead of am; both were in fact made in the morning.

Words you may meet

Diopsidae
The stalk-eyed flies. Small flies whose eyes sit at the ends of long stalks.
Diptera
The true flies. Insects with one pair of wings; the second pair is reduced to small knobs called halteres, used for balance.
Eye span
The distance from the tip of one eye stalk to the tip of the other.
Thorax
The middle part of an insect's body, which carries the legs and wings.
Femur
The thigh, the thickest segment of an insect's leg.

Related pages

About the photographs. Three frames by Wong Fook Yee with a Panasonic DMC-LX5, 5.1 mm, f/2.0, 1/60 s, on 13 July 2015 on the George Mais Trail at Bukit Gemok, Tawau, Sabah. The flash fired for the first two. The camera recorded the times as 21:25:50, 21:25:54 and 21:26:33; its clock had been set to pm instead of am, and the true times are twelve hours earlier. All three are camera originals that had never been opened in an editor. For this page the first has been reduced, and cropped and labelled for the close view; nothing has been sharpened, recoloured, added or removed. All three frames are on the iNaturalist record above.

The family characters and the account of eye-span contests, roosting and larval food are from the general entomological literature on stalk-eyed flies. The locality, date, weather and behaviour are the photographer's own. The plant is not identified. Distances from Tawau on this site are measured from the 0 km Tawau landmark using Google Maps. All photographs © Wong Fook Yee. Page written 29 September 2026.