You would not know, just by looking at this wasp – a Hairy Flower wasp – that it lays its eggs on beetle larvae living underground. Although the adults feed on nectar, the larvae feed on – are parasites of – the grubs of scarab beetles (Scarabaeidae). In some situations – because beetle larvae can be damaging pests – scoliid wasps can be useful biocontrol agents. The males are supposed to have longer antennae than the females, maybe this one – with its large black antennae – was a male? (See below). The mouth-parts are funnel-shaped..
Scoliid wasps like this one, a Campsomeris sp. (Family Scoliidae) burrow into the ground in search of white grubs (Scarabaeidae), or larvae, and sting them to induce paralysis. Quite how they locate the beetle larvae – which can be quite deep down in the soil – is something that would be fascinating to find out. When they have found it, they lay an egg on the beetle larva – sometimes constructing a special underground chamber for it. There is a picture here, of a paralysed dung beetle larvae, lying on its back with the tiny wasp egg attached to its abdomen. Quite amazing and perhaps a little gruesome? The wasp larva hatches out to feast on the larder provided for it by its mother. After a week or two of feeding, the scoliid wasp larva spins an underground cocoon and eventually emerges as an adult wasp, to start the cycle all over again.
The adult wasps are quite hairy (see photos directly above and below); which perhaps helps them to stay relatively clean when they burrow into the soil?
It is interesting to observe how the wasp is standing on the flower with four legs (below); but the back pair of legs are held aloft, out of the way. Sometimes an insect only needs 4/6 of its legs!
There are 10 species in this genus; I have no idea which one this is; photographed in Thailand (Chon Buri). They are not aggressive, but they do have a sting! They seem to get covered in quite a lot of pollen. These wasps are commonly seen in parks and gardens, as here (1).
- Soh, Z. W. W., & Ngiam, R. W. J. (2013). Flower-visiting bees and wasps in Singapore parks (Insecta: Hymenoptera). Nature in Singapore, 6, 153-172.