eTawau > Insects of Borneo > Wasps > A sand wasp at the Semarak football fields

The wasp that looked like a fly

A sand wasp digging its burrow in a heap of building sand beside the public football fields opposite Pasar Semarak, on a warm June evening in 2016

I often walk round the two public football fields opposite the Semarak Fresh Market in the evening. In June 2016 a heap of sand and gravel had been left beside them for building the new toilet, and on it a yellow-and-black insect was digging a hole. It dug at the entrance, flew off, came back a few seconds later and dug again, flew off for longer, came back, and kept on repeating it. I had seen wasps dig holes in the ground before, but I took this one for a fly, and I had never seen a fly dig. It turns out I had not seen one this time either.

A yellow-and-black banded insect with smoky wings folded flat over its back, standing at the dark mouth of a burrow in a heap of sand and small pebbles. A second burrow entrance is just to the right. Low evening sunlight throws long shadows from the pebbles. — **This is what you would see.** The sand heap beside the Semarak football fields, 26 June 2016, 5.40 in the evening. The wasp is at the mouth of its burrow; a second entrance is beside it.

Watch it work

Eight seconds at the burrow, 5.40 pm. The wasp digs head-first at the entrance, goes in, backs out, flies off, comes back a few seconds later, lands beside the hole and takes off again. Cut from the end of a 10.6-second clip, where the camera moves away; reduced to 1280 × 720 and the sound removed. Nothing else altered.

A wasp, not a fly

A close view of the insect at the burrow mouth, with six labels: the large eye; the burrow entrance; pale lines on the thorax; smoky wings, folded flat; yellow and black bands on the abdomen; and the pale legs. — **At the burrow.** Cropped from the photograph above and labelled; nothing else altered.

It is easy to see why it passed for a fly. It has big eyes, a stout body, and it moves in quick, darting flights. But look at the other photograph, taken two minutes earlier from above:

The same insect from directly above, much enlarged, with two labels: long antennae projecting forwards from the head; and pairs of black spots on the yellow bands of the abdomen. The thorax has thin curved pale lines. — **From above, 5.38 pm.** A small part of the photograph below, enlarged about nine times and labelled — which is why it is soft.

Long antennae. A fly's antennae are short stubs, usually hard to see at all. These stick well out in front of the head.
The wings. A wasp has two pairs and a fly one. Here they are folded together over the back and cannot be counted, so the antennae and the behaviour carry the case.
The behaviour. Digging a burrow in loose sand, then flying off and returning to it again and again, is exactly what a sand wasp does.

Sand wasps, tribe Bembicini, are solitary wasps that nest in bare sand. The yellow bands with pairs of black spots, the pale lines on the thorax, the big pale-green eyes and the habit of digging in loose sand all fit the genus Bembix.

How far the name goes. Sand wasp, tribe Bembicini, is safe. Bembix is probable but not determined: several genera of sand wasps look alike, and the genus and species are separated on details of the mouthparts, the wing veins and the underside that these photographs do not show. The record has been posted to iNaturalist, where specialists can take it further. Sand wasps were long treated as part of the family Crabronidae; most specialists now put them in a family of their own, Bembicidae, and that is where this page is filed.

Why it kept flying away

A female sand wasp digs a burrow for each young one and lays a single egg in it. Many Bembix species then do something unusual for a solitary wasp: instead of stocking the burrow all at once and leaving, the mother keeps feeding the larva as it grows. She hunts flies, stings them, carries them home and pulls them into the burrow, one after another, for days. Each time she leaves she closes the entrance with sand, and each time she comes back she digs it open again, often within seconds.

That is what the photographs and the video show: dig, go in, come out, fly off, come back, dig again. The short trips may have been checks or orientation flights; the longer ones, hunting. So the insect I took for a fly makes its living catching flies.

How big — not measured

There was nothing beside it to give a scale, so this record has no size. The pebbles in the heap are a rough guide only, because they vary so much. Sand wasps of this kind are usually somewhere between about 1 and 2.5 cm long.

Leave it to work. Sand wasps are not aggressive, and a female busy at her burrow takes no interest in people who stand still; like any wasp, though, she can sting if handled or trodden on. This one was photographed and filmed from a short distance and left to carry on.

The record

26 June 2016 · 5.38 to 5.40 pm · warm evening sunlight

Digging a burrow in a heap of building sand

The two public football fields opposite Pasar Semarak, Jalan Kuhara, Tawau, Sabah — inside the Tawau River Triangle, on ground that has been cleared and built over. The fields belong to the sports facilities of the Tawau Sports Complex; they lie outside the complex's compound, about fifteen minutes' walk from it. The wasp was on a heap of sand and gravel left beside the fields for building their new toilet. One wasp, not measured, alone, digging at the entrance of a burrow, with a second entrance a few centimetres away; flying off and returning again and again. Hymenoptera: Bembicidae: Bembicini — a sand wasp, probably Bembix; genus and species not determined. Two photographs, 17:38:50 and 17:40:38, and a 10.6-second video at 17:40.
— iNaturalist observation 404617783

A heap of sand and small pebbles lit by low evening sun, with tall grass on the right and, in the distance, the floodlight towers and grandstand of a sports stadium beyond trees. A small yellow-and-black insect is on the sand in the middle of the heap. — **The sand heap**, 5.38 pm, with the floodlights and grandstand of the stadium in the distance. The wasp is the small yellow-and-black mark in the middle of the picture.

Words you may meet

Sand wasps (Bembicini): Solitary wasps that dig their nests in bare sand. Most have big eyes and yellow or green bands, and many feed their young on flies.
Bembicidae: The family the sand wasps are now placed in; older books put them in Crabronidae.
Solitary wasp: A wasp that nests alone, without a colony or workers.
Progressive provisioning: Feeding a larva little by little as it grows, instead of leaving it all its food at once.
Hymenoptera: The order of wasps, bees and ants: insects with two pairs of wings, the hind pair smaller and hooked to the front pair in flight.

Tawau River Triangle — the ground around these football fields and the other records made there
Wasps of Borneo · The emerald cockroach wasp — another hunting wasp that stocks a nest for its young
Flies of Borneo — what it is not, and what it eats
Tawau Sports Complex — the football fields belong to it
Insects of Borneo

About the photographs and the video. Two photographs and one video by Wong Fook Yee with a Canon PowerShot SX510 HS, no flash, at 17:38:50 and 17:40:38 and 17:40 on 26 June 2016 beside the public football fields opposite Pasar Semarak, Tawau, Sabah. The photographs are camera originals that had never been opened in an editor; for this page they have been reduced, cropped and labelled, and nothing has been sharpened, recoloured, added or removed. The video has been shortened from 10.6 to 8.3 seconds at the end, reduced from 1920 × 1080 to 1280 × 720, and its sound removed. The still used as its poster is a frame from the video.

The account of sand wasp nesting and feeding is from the general entomological literature on Bembix, including Evans & O'Neill, The Sand Wasps (2007). The locality, date, weather and behaviour are the photographer's own. All photographs and video © Wong Fook Yee. Page written 30 September 2026.