The St Andrew’s Cross spider, Argiope keyserlingi, is very common in our gardens and it is named for its trademark, an “x” cross built into its web, this being the symbol of the Scottish patron saint. (Why? Find out here.)
This mid-sized female, however, wasn’t going to stop with an “x” but had added half of a central vertical stroke and a hint of the other half when I saw her yesterday. Her web is the same today, so that must be how she likes it. Why? No-one knows. In fact, no-one knows why spiders add any of these decorations to their webs.
The decoration, whether it’s a cross (as this ought to be), a loose squiggle (like this, created by a juvenile of the same species, or this, created by an adult of a related species) or any other shape, is called a stabilimentum. The new Whyte & Anderson Field Guide says, “proposed functions have included providing camouflage, making the web more conspicuous to prevent destruction, or attracting insects by reflecting UV light.”
Other orb-weaving spiders add different kinds of solid-looking components to their webs. Cyclosa species, for instance, construct a bar of prey debris across the centre of their web, in which they very deliberately camouflage themselves, but there is no guarantee that this behaviour is related to the Argiope species’ construction of a stabilimentum.
There isn’t much insect activity in the garden at this (dry, cool) time of year but when I was ambling around it last week I saw a Green Ant which was too small – only about two thirds of the size of a normal Green Ant.
That was my first thought, anyway, but a closer look revealed that it wasn’t an ant at all but a very good mimic. It is a juvenile Pod-Sucking Bug (Riptortus sp., Alydidae, Hemiptera) and in fact is the same species I described here on Green Path four years ago. That post shows older juveniles, gradually less and less like the Green Ant; this very small one turns out to be the best mimic of all, other than being too small.
This second image clearly shows its proboscis or sucking tube, tucked away beneath its body until needed.
As regular readers will be aware, I like spiders as well as butterflies and birds. I was very pleased when I heard the first hints that a new guide to them might be on the way, the more so since the author-to-be was my regular mentor in all things arachnological through his site Arachne.org and the Spiders of Australia flickr group. When he asked whether he could use a couple of my photos Continue reading “A Field Guide to Spiders of Australia”
My third visit to Wallaman Falls was a day trip with Wildlife Queensland. A full report will appear on their blog in due course but I thought I might quickly share this photo and mention my previous posts – from almost exactly one year ago and two years ago, as it happens. (This is a good time of year for camping and bushwalking, since everything is still quite green after the Wet but the weather is reliably fine and not too hot.)
I have added the spider and insect photos from this trip to my existing Wallaman Falls album on flickr.
Most of our largest butterflies are Swallowtails (Papilionidae), with the Cairns Birdwing (female wingspan to 150mm) and Ulysses (108mm) notable amongst them, but we also have smaller Swallowtails such as the Blue, Pale and Green-spotted Triangles (Graphium spp.) between 57 and 65mm. Most of the Nymphs (Nymphalidae) – Crows, Soldiers, Tigers, etc – are about this size, with wingspans between 50 and 65mm. Many of the Whites and Yellows (Pieridae) – Migrants, Jezebels and Albatrosses, for instance – are in the same range, too, while the others are all smaller and Skippers (Hesperiidae) and Blues (Lycaenidae) are smaller still. (Links on Latin names take you to collections of my photos on flickr.)
Swallowtails are named for the ‘tails’ which extend from their hind wings but not all Swallowtails have tails: Ulysses and Fuscous do, while others have mere tokenistic points instead of proper tails and the Chequered, Clearwing, Dainty and the Cairns Birdwing manage without any at all. On the other hand, many non-Swallowtails, especially Blues, do have tails.
What, then, are we to make of this handsome butterfly, with its 85mm wingspan and not one but two tails on each hind wing?
The historical range of the Lurcher (Yoma sabina, Nymphalidae) was always to the North of Townsville but, as I said last year, has recently extended to the city. At that time I had only seen a couple of blow-ins, but I’ve seen more since then and last week we had a group of four or five feeding on our bottlebrush Continue reading “Lurchers, naturalised”