eTawau > Insects of Borneo > Flies > A bristly fly on the Bombalai Hill road

A bristly fly on the buffer strip

A grey-and-black fly with a bristle-studded abdomen, beside the plantation road at the start of the Bombalai Hill trail, on a hot morning in September 2026

It came in, landed on a leaf at the edge of the road, sat for a few seconds and was gone. There was time for one photograph. Looking at it afterwards, the thing that stands out is the abdomen: banded black and silver, and studded, especially towards the tip, with long, stiff black bristles like the spines of a cactus.

A grey-and-black fly with clear wings held out at an angle, standing on a toothed green leaf near the tip of a shrub, with blurred green undergrowth behind. — **The only photograph.** Beside the plantation road at the start of the Bombalai Hill trail, 17 September 2026, 10.11 in the morning.

What it is

The same fly, enlarged, with six labels: long, stiff bristles on the abdomen; a clear wing; the grey-dusted thorax; bands of silvery dusting on the abdomen; a yellowish squama at the wing base; and a large reddish-brown eye. — **The same fly, closer.** Cropped from the photograph above, enlarged about twice, and labelled; nothing else altered.

It is a true fly, and it belongs to the Oestroidea, the superfamily of the blow flies, flesh flies, tachinid flies and bot flies. That is as far as the identifiers on iNaturalist were willing to go from one photograph, and it is a safe place to stop. What the photograph shows:

a thorax dusted with grey, with faint pale lines;
an abdomen banded with silvery dusting, carrying rows of long, stiff black bristles, longest towards the tip;
large reddish-brown eyes and a silvery face;
a yellowish squama — the little flap of membrane behind the base of each wing, which in this group is large;
clear wings held out at an angle, and long black legs.

How far the name goes. Superfamily Oestroidea is agreed. The likeliest family is the Tachinidae: strong bristles all over the abdomen are typical of tachinids. But some flesh flies and blow flies are bristly too, and the characters that separate them — the bristles on the sides of the thorax and the shape of the area under the scutellum — are not visible in a single view from above. The record stays at superfamily until someone can take it further. Sabah's tachinids and blow flies are described on this site's tachinid and blow fly pages.

If it is a tachinid

Tachinid flies are parasitoids. A female lays her eggs on, in or near another insect — very often a caterpillar, but also beetles, bugs and grasshoppers — and her larvae feed inside it until it dies. They are one of the biggest families of flies, and among the most useful to farmers, because they kill large numbers of plant-eating caterpillars. A bristly fly visiting the leaves of a regrowing roadside, where caterpillars feed, would be in exactly the right place.

How big — not measured

The fly flew before anything could be put beside it, so this record has no size. Flies of this build are usually somewhere between a house fly and a large blow fly in size.

Harmless. These flies do not bite. Tachinids in particular are friends of the gardener and the farmer.

The record

17 September 2026 · 10.11 am · a hot, sunny morning

On a leaf beside the plantation road

The first kilometre of the Bombalai Hill trail, the plantation road that starts just outside the Tawau Hills Park entrance, Tawau, Sabah — inside the 50-metre buffer along the protected forest, where the old oil palm is no longer replanted and the land is growing back. One fly, not measured, alone; landed on the leaf of an unidentified shrub, stayed a few seconds and flew off. Grey-dusted thorax; silvery-banded, bristly abdomen; large reddish-brown eyes; yellowish squamae. Diptera: Oestroidea. Family not determined, probably Tachinidae. One frame, 10:11:30.
— iNaturalist observation 404992354

The same walk

Eight minutes later, on the same stretch of plantation road, the same camera photographed a cotton stainer bug on a roadside mallow — the commonest insect on that stretch.

Words you may meet

Oestroidea: The superfamily of blow flies, flesh flies, tachinid flies, bot flies and their relatives.
Tachinidae: The tachinid flies: bristly flies whose larvae live inside other insects.
Squama: A small flap of membrane at the base of the wing; large in this group of flies.
Parasitoid: An insect whose larva feeds on a single host and kills it.

Bombalai Hill — the walk, and the 50-metre buffer it starts in
The cotton stainer from the same walk
Tachinid flies · Blow flies · Flesh flies
Flies of Borneo · Insects of Borneo

About the photograph. One frame by Wong Fook Yee with a Canon IXUS 285 HS, no flash, at 10:11:30 on 17 September 2026 beside the plantation road at the start of the Bombalai Hill trail, Tawau, Sabah. The camera original had never been opened in an editor. For this page it has been reduced, and cropped, enlarged and labelled for the close view; nothing has been sharpened, recoloured, added or removed.

The identification to superfamily is the iNaturalist community's; the account of tachinid biology is from the general entomological literature. The locality, date, weather and behaviour are the photographer's own. Photograph © Wong Fook Yee. Page written 1 October 2026.