Thursday, November 16, 2006

Spineless wonders

The WA Insect Study Society newsletter of February 2006 had a fascinating report from David Knowles, on creating a database of macro-invertbrates for the Greater Perth Metropolitan Region.
He gives an impassioned plea for invertebrates, and concludes with these fine words: The time has come when the culture of looking at biodiversity through a 2% vertebrate lens should be seen as anachronistic at best and plainly illogical at worst.
Here, here!

Just cast a look at this pie chart of species expressed as a percentage of the total of all animals found so far in Western Australia. And then remember that the vast majority of invertebrates are unknown and unnamed.

Monday, November 13, 2006

More confusing flies

There are masses of these insects about the place at the moment, as our unseasonally warm weather continues to encourage all the invertebrates to swarm about like it's February already. I fantasise that I live in Cairns and can almost see lightning cracking over canefields.

But I digress - at first glance I thought this was a tiny wasp, (it's appearing in sizes from tiny to small - 5-10 mm versions) it has all the right waspy colours and a nice wasp waist. Then a closer look made me see just two wings so I thought bee-fly. Then a very close look made me think

Hoverflies do the Batesian mimic thing very well, deterring predators by having that bee or wasp lookalike demeanour. Looking at a close-up of this flies wings, it's striking that the veins don't go all the way to the wing margin. This is characteristic of hoverflies, creating what is referred to as a "false margin". The other noticeable thing about this fly's wings is the scale over the halteres - a squama.
Here's a pic of a bee fly wing to emphasize the difference. This is the one from a week or so ago. It's a spectacular wing venation - just look at those lovely scrolls.

And here's a classic hoverfly wing - this is the introduced drone fly, Eriastalis tenax, the rat tailed maggot fly.

And here is today's fly. I'm not sure it's a hoverfly, so the mystery is still out there for the solving.

Sunday, November 12, 2006

More native bees

These tiny reed bees (Exoneura sp), are commonly found in the garden quite early in the season and all through summer into autumn. They really are small, hence the dodgy photo, only about 5mm. Obviously of an easy going and opportunistic nature as they are delighted with anything flowering, native or exotic (polylectic).
They are a long tongued bee, in the family Apidae, and enjoy visiting the Hebe flowers especially, where they can get the (very small) lion's share as the thin tubular Hebe flowers are largely inaccessible to honeybees.

Knowing that they like to nest in pithy stems I've carefully pruned everything in the garden so that plenty of likely nest sites are in the offing. Every year they've spurned my efforts with the local species of Kangaroo Paw, Anigozanthus flavidus, and I've never managed to sight them nesting anywhere. Not even in grasstree flowering stems, which I'm assured are their standard site.

Until this year - and true to their form (in the eastern states they like to nest in Lantana), they've chosen an introduced species, the very beautiful and luckily non-weedy South African Dierama sp. Every stem diligently left after pruning away last years' very tall fairy fishing rod flowers has been neatly drilled out and swept clean of sawdust, and occupied by one or more resident bees.
Exoneura are one of the semi-social (or semi-solitary, depending on your preference) bees, and two or more may occupy a nest and share chores. The larvae are tended and fed with pollen.

These were actually struggling for possession of this stem, sharing wasn't remotely on their minds. Short of ear tagging the bees I couldn't say which was the rightful possessor of the nest.

The other thing that's different about Exoneura is that they survive the winter, unlike most other native bees. Both the male and female spend the winter in the nest. And the cooler days, by the look of things, as they are only out and about when the temperatures are relatively balmy. So I can afford to get attached to these appealing little characters. Hurrah!

A nice article here
Aussie bees abuzz

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