Black weaver ants: call for sightings

Do you have black weaver ants on your property? If so, there is an entomologist eager to hear from you. Dr Mike Downes, who wrote this (first ever!) guest post for Green Path, has been studying them since 2009 and would like to hear from anyone who has these ants nesting in vegetation on their property. Here’s what he has to say about them:

Like green tree ants, black weaver ants, Polyrhachis australis, use silk from their larvae to bind leaves together forming a nest, most often in trees and shrubs but sometimes in artificial locations such as buckets or gaps in wall cladding. There are some excellent images on the internet of black weaver ants and their nests, including several on the Flickr photostream of Green Path’s author, Malcolm Tattersall. Here’s an example:

black weaver ants
Black weaver ants and their nest

The worker ants are shiny jet black, about half a centimetre long or longer, and forage singly. They only march in trails when relocating their nest. The nests range from about the size of a golf ball to as large as a pawpaw. The majority of nests have pale grey to charcoal-coloured, gritty walls constructed of plant and mineral debris bound together with silk. Occasionally, however, the nests are creamy-white and floppy, without much debris. In those cases, the ants are using an excess of spider silk instead of their own larval silk.

Disturbing the nest will usually result in a defensive outpouring of workers, but their bites are mild at most, barely noticeable compared with those of green ants. Also in contrast with green ants which have a single ‘royal’ nest and many outposts, black weaver ants have one or more queens in every nest, and lots of males too, especially between September and December.

Contact Mike on 47245616, mobile 0428194700,
email mikedownes@bigpond.com

Visiting White Mountains National Park

White Mountains National Park straddles the high point of the highway between Hughenden and Charters Towers. There is a lookout on the crest of the range – the Burra Range, part of the Great Dividing Range. It presents great views over wild country to the South of the road, but it is a bit sad that that is all that most people ever see of the park.

View from Burra Range lookout
Looking roughly South from the Burra Range lookout

Apart from the lookout, the park’s facilities are limited to a camping ground ten km off the main road, accessed by a dirt track recommended for 4WD vehicles only and comprising eight camping sites and a composting toilet, all neatly maintained in standard National Parks fashion (camping fees, in equally standard fashion, are a not-too-whopping $10 per night). There is no water supply, though, and the creek rarely runs so visitors have to bring all their own water.

The publican at Prairie reckoned my vehicle (a soft-roader, not a real 4WD) should have no trouble on the road ‘except for maybe the creek just before the campsite,’ so I cautiously gave it a go. The going was good until I got to the creek, which was only a trickle but its bed was deep soft sand perhaps four or five metres across.

view of Cann's Creek
Cann’s Creek just after the Wet – a trickle of water and lots of lovely soft damp sand

Walking across, I found I had the camp completely to myself and decided the possibility of a 10 km hike for help was less attractive than the certainty of a little extra walking, parked beside the track and carried my gear across to the campsite. After the tent was up, I had a quick look round then pointed my camera at the twilight sky:

Trees silhouetted against the sky
Twilight skyline, Cann’s Creek campground

Three things about the park struck me very forcibly: that it was a botanist’s paradise, that the vegetation was subtly but critically dependent on the geology (especially soil type and drainage) and that the animal life was completely dominated by ants.

I’m no botanist so I can’t say much about the plant life but I did enjoy all the flowering trees and shrubs, especially the wattles and grevilleas. This link will take you to a collection of my photos of them on Flickr.

As for the geology, it is all sandstone country – called the ‘white’ mountains for the pale grey-yellow of most of the rock – but the various sedimentary layers laid down over a couple of hundred million years are different in hardness and mineral content and have been exposed and weathered differently, resulting in a patchwork of micro-environments.

The clearest medium-size example was the area on the track to Sawpit Gorge which supported a veritable city of termite mounds (here and here). On a much smaller scale, I found an isolated patch, less that a square metre, of sundews beside the track near the Sawpit Gorge lookout:

Sundew plants in sandstone gravel
Sundew plants in sandstone gravel

There must have been a tiny seepage of moisture from up-slope, to encourage them here but nowhere nearby. (A better view of individual plants is here.)

As for the ants, I had camera problems (reduced to a point-and-click by battery failure on the SLR) so I didn’t try to take many pictures of small subjects but I did record some of the amazing variety of ant-hills along the road.

The guide to the park is replete with warnings about waterless, trackless wilderness and the very real chance of getting lost or injured. Roaming around the park is recommended only for ‘experienced, well-equipped bushwalkers’ in strong parties. However, a walk along the road from the highway to Sawpit Gorge and back (or a shorter part of that trip) would be a very easy, enjoyable and safe way of seeing a good selection of what the park has to offer. Camping a night or two at Cann’s Creek will be possible for most people, most of the year  (it’s not recommended in the Wet) and offers a complete break from urban life as well as an extended opportunity to explore the diversity of the area.

Park information: http://www.npsr.qld.gov.au/parks/white-mountains/about.html

Related posts on Green Path: Easter break, Life in ‘the outback’ (more to come).