Walking in the Paluma rainforest

Paluma Dam track
The walking track

A recent trip to Paluma Dam with the good people of Wildlife Queensland was enjoyable for the wildlife and just being in the rainforest but was far from strenuous. We walked across the dam wall and along a vehicular track to the west of the dam, took a side track to down to the dam shore, and returned the same way before lunching at the camping ground. Birds were constantly audible but frustratingly invisible, so most of my photos are of invertebrates.

Paluma Dam forest
Looking into the forest below the dam wall
Paluma Dam
Looking across Paluma Dam

These two butterfly species were the commonest on the day but are unfamiliar around Townsville. Braby notes that both are ‘common but local’ in their territory, the Wet Tropics. The upper wing surfaces of the Grey Albatross are white and pale grey with darker wingtips, so both shone out brightly in the shadows of the forest.

‘Puddling’ is the proper term for butterflies’ habit of landing on wet sand (as here) or beside shallow puddles (as here) to suck up some water.

These two spiders were both found in the camping ground, one on our picnic table and the other on the brim of a hat. The brown one is certainly Tetragnatha sp. but even the new Field Guide to Spiders of Australia calls it ‘unidentified’.  The green one? I suspect it may be a Mesida, in which case it belongs to the same family, but I’m not at all sure.

A miscellany.

Robber flies are aerial predators like dragonflies – note the huge flight muscles – but are ‘real’ flies unlike dragonflies or butterflies.

The hopper, a sap-sucker (Hemiptera) only about 5mm long, looks like it’s standing on something coarse and wiry but that’s only because of the magnification. In real life, the leaves are beautifully velvety.

leaves at Paluma Dam
Soft new foliage – gorgeous!

The ant that wasn’t

ant-mimicking jumping spider
Crawling on the edge of an outdoor table

Sitting in the back garden yesterday, I glanced down to see an ant wandering along the edge of my table – or so I thought. But it wasn’t moving like an ant: they are purposeful, even if we may not divine their purposes, and this maybe-not-an-ant was wandering rather slowly and aimlessly. At a closer look, its antennae weren’t very convincing, either Continue reading “The ant that wasn’t”

The individualist

St Andrew's Cross spider
St Andrew’s very cross?

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? Continue reading “The individualist”

A Field Guide to Spiders of Australia

Cover of A Field Guide to Spiders of Australia

A Field Guide to Spiders of Australia

Robert Whyte and Greg Anderson

CSIRO publishing, 2017
Paperback $49.95; e-books also available.

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”

Spider explosion

Mangroves covered in spiderweb
Mangroves covered in spiderweb

I stopped off at one of my inner-city parks three weeks ago and saw the biggest spider colony I’ve seen for quite some time. I was more than slightly boggled by it. Skeins and swathes of web stretched from one mangrove tree to the next along at least 20 metres of creek bank, overhanging the water and within about 1.5 m of water level. (It’s the bank on the far side of Ross Creek from these cormorants.)

Looking into the web ...
Looking into the web …

When I looked more closely I saw long skinny orange-brown spiders (1), lots of smaller chubbier charcoal-white patterned spiders (2), and a few very small ones (3); also lots of egg sacs woven onto twigs.

I reckoned that (3) were very young juveniles, that most or all of (2) were sub-adults and that (1) were adults, all of one species. “Which species?” is the obvious question. Not so obviously, why did all the adults I photographed happen to be males? Do sub-adult males change from type (2) colours to type (1) with their last moult, I wondered, while adult females remain type (2)?

Identifying the adults to genus level is easy, since the enormous jaws are very distinctive. They are in the genus Tetragnatha in the family Tetragnathidae. Both genus and family have the common names ‘Four-jawed Spiders’ (an exact translation of Tetragnatha) or ‘Long-jawed Spiders’. Beyond that, identification is less certain. They may be Tetragnatha nitens, T. rubiventris or another close relation (follow this link for photos of each species).

On a second vist two weeks later I saw many adult females with the reddish coloration, so any gender imbalance was only temporary. The webs were just as extensive and the egg-sacs even more numerous, although spider numbers seemed to be a little reduced.

I normally see adult spiders in this family as individuals (e.g. this collection), often well away from water and often with hardly any web, let alone a tent city like this. The expert I call on for things arachnological suggested that this could be a local ‘population explosion’, for whatever reason. He hadn’t heard of it with this genus but says it does happen with others, mentioning one of the St Andrews Cross species as an example.

What will happen here remains to be seen. I will call in again and report back … if I emerge alive. I’m just joking, of course – they are completely harmless, and the biggest risk to me is that I will fall in the creek while trying to take a better photo.

Tetragnathidae
Part of the web on my second visit