Wednesday, 31 January 2007

Fan—flower—dango

The leaf-cutter bees (Megachile) were making hay in the fan flowers today. When I first caught a glimpse of a fine-banded bum disappearing into the vegetation, I thought it was a hoverfly. But then I spotted the front end with its angled antennae and the punky orange topknot and I recognised my visitors.

They're flighty insects, settling for a second or two before zipping off to the next blossom. So industrious are they, they make honey bees look like slackers. It's almost impossible to photograph a leaf-cutter when it's feeding (although Amegilla managed to do it. Check the link above for splendid pics). The best time to take a picture is while it's snipping out pieces of foliage for the nest. Unfortunately—or perhaps not—none of the plants in my garden have suitable leaves, so the bees drop in for meals but go elsewhere for their furnishings.

While attempting—and failing—to get a decent shot of these pretty and unpredictable insects, I noticed another little lovely. A real hoverfly this time and one much more amenable to having its portrait taken than were the busy bees.

As an adult, the drone fly (Eristalis) is a handsome animal. It's less attractive in the larval stage, when it lives underwater and bears the epithet 'rat-tailed maggot'. The name is half-right. As a fly larva, it is a maggot. There's no getting around that. But the rat tail is a respiratory siphon that extends from the larva's rear end to the water's surface. Although it is aquatic, it can't extract oxygen from water, so has to rely on a snorkel on its derriere.

Rat-tailed maggots prefer water that is rich in organic matter, like ditches and ... er ... sewage farms. This makes me wonder where this adult might have started its life. Perhaps they travel some distance after emergence. Or perhaps a neighbour's water feature needs a bit of treatment.

The maggot's affinity for sewage has occasionally brought into contact with humans—and not in a good way. Its unexpected appearance in toilet bowls may result in a panic, especially when conjecturing about the way in which it got there. One path (incoming via a septic tank) is more likely than the other (outgoing via ... let's just say they might be going through the motions). Either way, a rat-tailed maggot is not something you want to see in your lav.

But I digress. Back to the adults on the fan flowers. They look and behave like bees but are completely stingless. They're distinguishable on their tiny antennae (you can't see them on hoverflies but they're small but obvious on bees) and the shape of the eyes.

They also look a bit like March flies (Tabanidae) but don't bite. You can tell them apart by the eyes (in March flies, the eyes are very close together along the midline) and—we're getting into detail now—by the false margin along the rear edge of the hoverfly wings. A false margin occurs when the veins don't run all the way to the wing edge, leaving a clear cell.

But that's not all the wildlife on the fan flower at the moment. The skippers are loving it. More of them later. And to think I was going to cut it all out. Maybe after it stops flowering ...

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