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Unusual web-building behaviour in the Redback Spider, Latrodectus hasseltii
Invertebrata 7, Spring/Summer 1996/97

A sub-adult female redback spider was collected in March 1996 for display in the live spider display at the QVMAG. She was collected from underneath the rim of a large black plastic pot plant container.

Once she was placed in the display she began to build a web between sticks that had been placed in the display for that purpose. The display consists of a transparent perspex box divided into six cubicles. The divisions are also transparent.

Within a few days, pieces of substrate began to appear in the web to form a triangular shelter under which the spider could conceal herself. Pieces of substrate included small rocks up to 11 mm in diameter. The shelter was not used continuously. The spider would suspend herself outside of the shelter unless she was disturbed by any vibration and then she would quickly retreat under the shelter.

Several other specimens have been kept in this display and this behaviour has not been observed. Redback spiders in the wild do not appear to construct shelters and where debris is apparent it has been attributed to wind deposition (R. Raven, pers. comm. 1996).

Louise McGowan
Research Officer, QVMAG

Land nemertines for fun and profit
Invertebrata 7, Spring/Summer 1996/97

In Invertebrata 1 I wrote about the land nemertine Argonemertes australiensis, which I described as looking like an overweight flatworm. I also gave references to what I called the 'small but informative literature' on this species. Well, maybe not so informative - surprisingly little is known about the biology and day-to-day life of A. australiensis. The world expert on land nemertines is Dr Janet Moore of the Zoology Department, University of Cambridge (UK). Last July I visited Dr Moore (an Invertebrata subscriber!) and asked whether she could suggest any questions about A. australiensis that could be answered by naturalists in Tasmania, where the worms are common and fairly easy to find. The result was a feast of do-it-yourself biology:

Captive worms. 'I think the most valuable thing is simply to keep them alive in the lab and see what they do. Nobody has done this for ANY land nemertine.' Night-time observations with infra-red (or weak red?) light will be necessary, since the worm'' likely to be strictly nocturnal. They also require high humidity - a cage with a floor of damp (but not dripping wet) rotting wood or Kleenex tissues (easier to change when mould appears!) might be OK.

Early development. The egg capsules (I've found them in rotting logs in August and March) are clear, jelly-like objects about 10 mm long and 3 mm in diameter. How long do the eggs take to develop? Do they all hatch at once? What triggers hatching?

Hatchlings and adults. What times of the day are they active and for how long? What, when and how do they eat? (Nemertines are believed to be predators that feed mainly on soil arthropods.) What range of temperatures, humidity, light regimes etc. keeps them happiest? What sort of oxygen consumption do they have at rest and when active? Can lab results be confirmed in the field? (For example, if they're lab-active from midnight to 3 a.m. in midsummer, are they forest-active from midnight to 3 a.m. in midsummer?)

Later development. As Argonemertes get older they get longer and heavier and have more eyes, but there isn't a growth chart yet for these or any other features. One is needed!

Colour. As I mentioned in the earlier Invertebrata article, there are distinct colour varieties for this species in Tasmania, often with several at one locality. Genetics could be tricky to study, but do all colour forms come out of one egg capsule or only one? Dr Moore wants to know why land flatworms and nemertines often have similar markings. 'Who is mimicking whom and why? Who can ever see the beasts anyway - a nocturnal predator with infra-red vision?'

Gelatinous cocoons. Two other Argonemertes species secrete these structures and shelter in them when conditions are adverse. A. australiensis hasn't yet been seen to make such a cocoon. Does it?

Parasite infestation. New Zealand land nemertines are sometimes heavily parasitised. Are ours? Could it be that the parasite changes the behaviour of its host, bringing it out of hiding so the parasite can complete its life cycle, as happens with some snail parasites?

Lots to learn! For information on what little is already known, see that small literature:

Hickman, V.V. 1963. The occurrence in Tasmania of the land nemertine, Geonemertes australiensis Dendy, with some account of its distribution, habits, variation and development. Papers and Proceedings of the Royal Society of Tasmania 97: 63-77 + plates.

Winsor, L. 1985. The land nemertine Argonemertes australiensis (Dendy) in south eastern Australia. Victorian Naturalist 102: 28-36.

Bob Mesibov
Research Associate, QVMAG

Around Australia in 22 days
Invertebrata 7, Spring/Summer 1996/97

Professor Norm Platnick, post-doctoral fellows Drs Vladimir Ovtsharenko and Kefyn Catley, all from the American Museum of Natural History, arrived in Brisbane on 19 November. They are running on PEET and ABRS grant funds and are working on ground-hunting spiders of the superfamilies Gnaphosoidea and Clubionoidea. They were based in Brisbane and I accompanied them on field trips to north Queensland, New South Wales, Western Australia, Darwin and Victoria. They may also be visiting other State natural history museums in Canberra, Melbourne, Adelaide, Perth and possibly Darwin.

The really exciting news is that during this trip we tried the David Hirst vibration method (after seeing 'vibration' as the method of collection on so-o-o many spiders in the museum in Adelaide).

We were at York, WA. We had Barbara York Main, Julieanne Waldock, Mark Harvey, the AMNH crew and myself (seven of us). We searched for 1½ hours and got little, despite the litter on John Bannister's property, which had not been burnt, being about 3-4 inches deep. Amazing! Mark got back and remembered to start up the diesel troop carrier. I was standing on the litter at the time and my God the litter boiled with spiders! They didn't home on the vehicle much but just kept coming up and running around. After about 20 minutes we were glutted and moved the car about 5 m and kept going. In all we stayed about 40 minutes. I got over 60 spiders, many mature. The rest got more because after I stopped remonstrating and got my composure I ran off to get the video but the effect was now less dramatic. We were all in shock and exhausted. Spiders were still moving but we were truly glutted. The range of effectiveness was 15-20 m, Amazing stuff. Sadly, it did not work later in bushland sand. Hopefully, we can do something similar by pulling a lead off a spark plug of the Falcon in the north. This revolutionised my thinking about sampling. We have to isolate the frequency and amplitude and figure out a portable 'truck'.

On returning home and trying this method with various measures of success, we are looking forward to David Hirst's formal exposition of how to get it to really work well.

Dr Robert J. Raven
Museum Scientist (Arachnology)
Queensland Museum
PO Box 3300
South Brisbane QLD 4101

Current research on Onychophora
Invertebrata 7, Spring/Summer 1996/97

A six-month study of the egg-laying velvet worms (Onychophora) of Tasmania is being funded by the German Scientific Foundation. This PhD project will study the morphology, anatomy, development and biology of oviparous Onychophora. Morphological and anatomical examinations will be undertaken with the intention of clarifying the taxonomy of the Ooperipatellus insignis complex. This complex contains 11 species, only two of which have been described (Ruhberg 1995). Live specimens of three Ooperipatellus species are being kept in the laboratory for observation.

An 'onychophoran-swarming' was observed in the Fingerpost area, about 8 km east of Waratah (NW Tasmania) on 12 October 1996 with Bob Mesibov. Approximately one hour after sunset 20 specimens of Ooperipatellus decoratus were found climbing up tea-trees (Leptospermum lanigerum). They had dispersed 30 minutes later. This 'swarming' has been observed once before by Bob Mesibov in the same locality on 18 October 1991.

Claudia Brockmann
Zoologisches Institut und Zoologisches Museum
Universitaet Hamburg
(Currently at QVMAG)

Reference:

Ruhberg, H. 1995. Zur Systematik, Biologie und mikroskopischen Anatomie der Onychophora, insbesondere der Peripatopsidae Tasmaniens. [Forschungsbericht zur kumulativen Habilitation des Fachbereiches Biologie der Universitaet Hamburg; unpublished, 42 pp.]

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