[update] – When I wrote this I thought the creature was a robber fly, now I think it’s a spider wasp.

Here’s something you don’t see every day, a large fly like creature walking along carrying a sizeable spider underneath it! Now that’s a prey reversal! A bit like seeing a huge rat hauling a dead cat somewhere.

The fly was black, about 4cm in length with long legs that allowed it to carry the spider underneath it and still walk easily. The one I saw was on a mission to get somewhere, it walked quickly over the pavement for about 4m and then climbed a wall before I lost it. It had wings but didn’t try to fly, maybe the spider was too heavy for it. The spider was slightly longer than the fly and looked bulkier, all the spiders legs were gone and it was being carried inverted with it’s abdomen towards the front of the fly.

Curious as to if this was normal I did some searching. The closest thing I could find that lives in the area is a robber fly. “Robber flies are large, bristly flies that catch their prey (usually other insects) mid-flight.” Robber flys are known to catch and eat spiders, the fly I saw didn’t have the same enlarged powerful chest as the robber fly photos on the articles. It looks like there is some variation between robber fly species so maybe it’s just a different species that I saw.

It was moving fast and I only had my phone on me so I found it hard to get a clear picture, but you can see the size of the spider compared to a garden hose and a house brick. The spider looked like a huntsman, I’m not sure how the fly would have killed it and removed it’s legs, or maybe it found the spider like that?

Resources and references

• Wikipedia
• Brisbane insects
• Australian Museum