The burrowing wasp

We’ve had a couple of big mounds of mulch in our garden since the stump-grinding people did some work for us almost a year ago. “Leave us some mulch,” I said, and they did.

We have gradually spread it around and dug it in, but we’ve had a surprising amount of help from little friends – mostly big fat white grubs which are scarab larvae.

A big black wasp has been keen to help, too.

Flower Wasp
Wasp digging into the mulch
Black Flower Wasp
Almost gone

I’ve seen one several times in the last couple of weeks, flying up out of the heap as we disturbed it, or circling before landing and digging, but I haven’t managed a clear shot of it on the surface. This old photo, however, probably shows the same species.

As I said at the time, it’s a Hairy Flower Wasp, Scoliidae (I haven’t been able to identify it to species level but the genus is Scolia). They are “flower wasps” because the adults feed on nectar, as this one is doing. (It’s in the same genus but is not the same species – note the absence of yellow spots on the abdomen.) Their larvae, however, parasitise scarab grubs, so my wasp was digging down to lay eggs.

Our most common adult scarab is this beautiful metallic green creature. It’s in the scarab family, as are so many of our largest and most colourful beetles. I know it’s in the subfamily Cetoniinae – Flower Beetles – and it seems likely to be Ischiopsopha wallacei but I can’t be quite sure. In any event, its larvae have been very helpful in breaking down our mulch and are the likeliest targets of our wasp.

green scarab beetle
The beetle whose larvae are the target

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