writer and photographer SIMON GROVE
When my mother-in-law, Norma, passed away, part of her legacy was a second-hand campervan bought with the share of the estate that flowed to her daughter – my wife, Chris. Norma had led an adventurous life, and it seemed fitting that Chris named the van “Norma” in her honour – affixing a sticker featuring her signature to its paintwork.
One recent September, I drove Norma from Hobart to the Tarkine rainforests, in the far north-west of Tasmania. Ostensibly it was to set up some insect traps, under permit, in this understudied region, since Tasmanian invertebrates are both my passion and my profession. The traps were also part of my cunning plan for spending quality time there over the ensuing summer, since I would need to service them every month.
The rainforests of the Tarkine/takayna feel timeless. With soft, springy ground accommodating one’s footsteps without audible complaint, it’s easy to walk through them in noble silence. Some call such an experience “forest bathing”. It offers exhilaration without undue energy expenditure. It’s a winning combination, and an enticing prospect, and one for which I am willing to traverse the entire state in a campervan to experience.
I arrived at dusk. I brewed a cuppa, and allowed myself to unwind into the sights and sounds of the rainforest and a babbling creek, just metres from where I had parked. A fat-bottomed pademelon, skulking among the sedges at the edge of the clearing, pretended to graze but was really just biding its time in the vain hope that I might throw it a tastier morsel. A black currawong began its discordant, yet slightly mournful, evening call from the top of a dead myrtle, a sort of winding-down routine, bookending the day in preparation for roosting. At some point, it decided enough was enough. Then the only sound was the creek, continuing its babbling unabated.
As a starry night closed in around me, my mind played unsettling tricks, turning the murmuring of water over well-worn pebbles into snatches of speech, laughter, singing and crying. How easy it would be to attribute agency and animacy to the mysterious source of these sounds. Maybe I should? The spirits of the ancestors, perhaps; or the creek itself, striking up conversation with the trees, or with me. It would have plenty of tales to tell, I’m sure. All things seem possible when you’re alone in a dark, timeless rainforest. It put me in a jittery state of mind as I bedded down for the night.
Mercifully, though, the night was uneventful – or I was too tired after my drive to notice – and no dark spirits manifested. The morning brought clear skies and the prospect of some springtime warmth. The murmuring creek had shrugged off its nocturnal air of malevolence, and I watched its tea-stained waters for a while as I ate my breakfast. Dollops of foam sailing by told of rapids upstream, but here the creek’s flow was merely turbulent and, to my mind, deeply relaxing.
But there was work to be done. I donned my backpack and followed the track down a muddy bank into the rainforest, inhaling deep breaths of humid air and savouring its earthy aroma. It was serene and rather lovely, with widely-spaced, gnarly old myrtles, scaly-barked; here and there girdled with oversized bracket fungi.
Interspersed among the veterans were younger myrtles, leatherwoods, sassafras, treeferns and the odd blackwood. The forest floor bore a veritable shag-pile carpet of emerald-green mosses and leafy liverworts, and every log and stump was similarly draped. Treeferns, too, were festooned with mosses, filmy ferns and tassel ferns.
To the pleasant acoustic accompaniment of jingling pink robins and the liquid, warbling purr of Tasmanian thornbills, I scouted for a spot to set up the first of four traps, out of sight of the path. I soon found what I was looking for: a sheltered glade hemmed in by shrubs and treeferns. I was using a Malaise trap, which features a vertical screen of fine, dark netting, invisible to flying insects; this is suspended beneath an integral, tent-like roof of bright, white netting, higher at one end than the other. At the high point, a hole leads to a collecting chamber, which is filled with ethanol as a preservative. Guyed and pegged out, such a trap can be left sampling for weeks, during which time legions of small flying insects might fly into the netting, heading upwards towards the light and dropping into the pot of ethanol.
Yes, it’s a sad fact that to identify most insects, some killing is unavoidable. Once I had found secluded spots for all four traps, I retraced my steps, tuning in to a distant bassian thrush which had struck up its quiet, fluty and rather soulful song –eminently suited, I felt, to a bird that likes to lurk in the darkest recesses of the rainforest, as I sometimes do, too.
At the end of summer, I again drove Norma along the now-familiar route to the enchanted rainforest and retrieved my traps. Whilst it was a wrench to leave for the last time, I was looking forward to sorting through the samples at my Rosny workplace, the zoology research collections for the Tasmanian Museum and Art Gallery. I was anticipating all kinds of interesting finds that I might then separate out for pinning, identifying and adding to the state collections.
And I was not disappointed: there were flies, bugs and beetles aplenty – several hundred species of them.
One dark, elongate and rather exquisite fly, about a centimetre long, stood out from the crowd and piqued my interest. It was a hoverfly, but not one I had seen before. Six individuals had ended up in the samples. I recognised them as members of the leaf-walker genus, so-named for the fly’s habit of scouring the surfaces of leaves to vacuum up tasty grains of errant pollen, whilst eschewing the flowers that attract other hoverflies. Leaf-walker larvae live in rotting logs (including waterlogged ones), and so the flies are often associated with wet forests and tree-line, debris-choked creeks.
Yet this fly wasn’t the Australian leaf-walker (Xylota flavitarsis), which is widespread across Tasmania and the only known member of its genus in Australia. That species sports yellow feet (hence flavitarsis), whereas those of “my” flies were blackish, albeit dusted with yellowish scales. More obviously, the basal two-fifths of each hind femur were lemon-yellow, contrasting with the blackness of the rest of their legs; those of the Australian leaf-walker are entirely dark.
I sent photos to a Canadian hoverfly taxonomist, Jeff Skevington. Skevington has a comprehensive knowledge of Australian hoverflies, and of the global leaf-walker fauna, having recently described two new species from North America (there are 131 globally). He confirmed what I had suspected: I had a new species!
Finding obscure new insect species in Tasmania is actually not that unusual; finding a distinctive new hoverfly species, rather more so, because most such species were discovered long ago. I resolved that, with Jeff Skevington, I would formally describe and name it, as new to science. This would require documenting the vital statistics of the sole male specimen, which I would designate the “holotype” – the unambiguous, all-time physical representation of its species. I would need to dissect and photograph its genitalia, which in insects are often diagnostic, differing markedly among otherwise very similar species. Though this wasn’t necessary for distinguishing my new species from the Australian leaf-walker, if anyone came across another putative new species, they might need to compare the genitalia for confirmation.
Under Skevington’s expert guidance from afar, I practised my dissection skills on some of the many Australian leaf-walker specimens in our museum collections, before plucking up the courage to work on our holotype. I softened the pinned specimen in a humidifying jar overnight, then teased out the terminal abdominal segments with a micro-pin. I soaked these in hot lactic acid for several hours to soften and part-dissolve the outer integument, and then transferred the all-important, sub-millimetre-length genitalia into a drop of clear glycerol. At various stages in the subsequent dissection, I employed our automated microphotography setup to take scores of photos at different focal planes, combining these on a computer into high-resolution images in which the entire subject was in focus. Eventually I had what I needed to incorporate descriptions and illustrations of the various parts of the genitalia into the paper. The dissections were returned to a capsule of glycerol, mounted on the holotype’s pin.
All that remained, before submitting the paper for peer review, was to give the fly a scientific name. I thought back to my time in the Tarkine rainforests, and to the campervan that had made my visits such a pleasure; and to Norma, after whom the van was named. And then I knew: I would anoint my hoverfly with the specific epithet norma. Norma the Tarkine leaf-walker. I think the original Norma would have liked that.
Dr Simon Grove is a Hobart-based naturalist, zoologist and author. This article is a adapted from his new book, Seasons in the South: a Tasmanian naturalist’s journey of discovery – and recovery, illustrated by nature artist Keith Davis, and published by Forty South.
