When I was at the Barren Grounds yesterday, with a group of birdwatchers, we were distracted by a strange looking Ant-like creature walking (almost running) all around the picnic table in the shelter shed there.
I could not get a good fix on what kind of creature this was, at the time. It moved fast, by walking quickly on its distinctively long legs. It looked like an Ant. But was it? Could it have been a wasp? Or even a Spider? There are Ant-mimicking Spiders, after all.Just in case it might have been an aberrant Spider we decided to check the number of legs, and came up with an odd number - literally an odd number. It appeared to have only 5 legs, and that always makes it hard to work out what kind of creature it is, for obviously it has been damaged, as often happens in Nature. I recall a Phasmid (Stick Insect) I once found which is famous for having a "sacrificial" strategy, of losing limbs, or parts thereof, in order to allow the insect to survive attacks by birds - a similar strategy is used by Skinks, of course, which readily shed their tail tip, but can survive such an attack and even re-grow a new tip of the tail.
As someone who once thought seriously about buying a 5 cylinder Audi, I am always intrigued by such seeming imbalance. But I digress.
The clue to the identity of this creature is here. At full resolution the head shot shows a distinctive shadow (from the flash).See what I mean? The v-shaped protrusion is typical of a Fly. As a matter of fact, you can even check out David's wonderful shot of a Hoverfly, and see a similar antenna structure on its face. As soon as I spotted that v-shaped shadow, I checked the positive image itself, and realised I was staring a fly's face. Even the red eyes on each side of the head became obvious as typical fly eyes (obvious once you work out what you are looking at).
But it was the shadow of the short antennae which swung it for me. You see wasps and bees (related creatures - Hymenoptera) both have prominent mid-sized antennae which are distinctively bent ("elbowed" as Peter Chew refers to it). By contrast, Flies (Diptera) have very short, straight antennae - which is what I had noticed.
From that moment on, it was simply a question of searching the available internet references.
I started with the wonderful Chew Family's Insects and Spiders of Brisbane. That took me to the prospect of it being a "Stilt-legged Fly". I followed a further link to Nick Monaghan's "Life Unseen" website. and I found that it was indeed a "Stilt-legged Fly" - indeed he has a 'dead ringer' for my insect, under the name of Metopochetus sp.
So, that reminds me of the old joke: "When is a fly, not a fly? When it is a Walk!"
In all the time we watched this creature, running around the picnic table, crossing large gaps between the rustic boards on the table, etc, it never attempted to fly. That's why we thought it was an Ant. Indeed its transparent wings were held so close to the body (not widely spread, as in many flies), that the wings simply looked like a metallic sheen on the body of the insect.
Just to help clarify the shape of the insect, I spent some time on Photoshop, removing the shadows (because I had photographed it with the flash, on a Macro setting). In a sense it was just as well I did, as it was the shadow which gave me the clue as to the identity of this creature, as I mentioned. But the true shape of the insect is more clearly visible now, once the shadows have been removed.
I still think it looks like an Ant - but I am convinced that it is indeed a Stilt-legged Fly.
But with 5 legs, it might just be an "Audi-fly".
By the way, it was almost impossible for me to get a really clear focus on this creature, as it ran around the picnic table. These days, I only have manual controls on my Micro lens (A control ring on the Micro lens has broken). So just consider how amazing is David's achievement to snap that hoverfly in perfect focus, when in flight? No wonder his blog is called "Focus on Nature".