Hunting asexual grasshoppers in western NSW, and retracing some famous footsteps

On the 19^th February Vanessa, Anwar and I did a field trip to collect specimens of the parthenogenetic matchstick grasshopper Warramaba virgo for genetic material. We recently developed some powerful nuclear markers that should give us some conclusive data on how this grasshopper evolved. But we needed some fresh material so off we went in a Kia Carnival, up the Calder Hwy.

Day one – Melbourne to Broken Hill

The first stop was near Bendigo in a heathy open woodland, where we were looking foranother kind of matchstick grasshopper – Vandiemenella viatica. We have been checking this place regularly to get an idea of their life cycle. They are reported to be a winter species, hatching some time in the summer and maturing over the winter, finally laying eggs in spring. We found the grasshoppers to already be around 3^rd to 4^th instar – older than we expected. They were all found up in Cassinia bushes, which we shook into hoop nets to capture them.

Second stop was also in Victoria at another V. viatica site, 20 km North of the town of Ouyen (famous for vanilla slice). This mallee site is at the inland extreme of the species’ range, and here you can find them by walking slowly looking amongst the forbs and Triodia clumps. Ian Aitkinhead and I found them to be quite sparse and at final instar in mid September last year. I then failed to find any in early October. This time we found them to be even further developed than the Bendigo specimens – 4^th to 5^th instar. So they must have been right at the end of their life cycle in September – interesting data!

The third stop was Yatpool, an old W. virgo site. We shook a lot of Senna bushes but no grasshoppers – quite a few mantids though (perhaps that’s where the grasshoppers went).

We moved on to a site about 100 km N of Wentworth and finally caught some W. virgo, on Senna. However, this site, which I collected from back around 2006, had been badly damaged by the installation of a high-pressure water pipe that appears to run from Wentworth all the way to Broken Hill, leaving a trail of broken, roadside remnant vegetation all the way.

Our final stop for the day was near the sheep/cattle station Netley – sold for over $10,000,000 in December last year it turns out. Here W. virgo can be found on the beautiful Acacia loderi, which has needle-shaped leaves. We collected on dusk and watched the ‘super moon’ rise. We also collected after dark by spotlight. The grasshoppers are quite easy to see this way and kick their hind legs when the light hits them, a behaviour usually applied to unwanted males. This lineage of parthenogenetic females hasn’t had male Warramabas bothering them for sex for tens to hundreds of thousands of years but they still retain this kicking reflex. However, there is another genus of matchstick grasshopper that lives with them, Capsigera, and the males of this species probably annoy the parthenogens from time to time.

The drive between Mildura and Broken Hill was striking for how dry the country was. I have driven this road over a dozen times and have never seen it in in such bad condition – a thick layer of dust and sand was covering most of the landscape and there was very little vegetation. There were lots of very well-fed looking goats however. We were also flagged down by a sheep valuer and his dog, who had broken down after driving all night (and “having a few roos run into him”). He was meant to be in Echuca that day but his battery wasn’t going to allow him to drive the remaining 600 km!  We texted his predicament to his boss once we got reception near Broken Hill.

Day two – Broken Hill to Cobar

On the 20^th of February we collected around the town of Broken Hill. This site, Stirling Vale Creek just west of the town, was an old site of Michael White’s from back in the 1970s. They feed on the mulga tree here, Acacia aneura, as well as A. loderi. I have been collecting here many times since but was dismayed to see that most of the mulga trees I used to collect from had been chopped down for no obvious reason. Fortunately, we were able to find some on A. loderi nearby.

We then continued to Hazel Vale, near the truck-stop ‘Little Topar’. This was our main target site because a large sample of W. virgo had been analysed for clonal diversity using allozymes by Honeycutt and Wilkinson back in the 1980s. It was not easy collecting but after over 2.5 hours we had over 20 specimens. It was a luxury to be able to drop in for a cold drink and a hamburger at Little Topar midway through collecting.

We then collected at the turnoff to the town of Ivanhoe (recently featured in a story about struggling rural towns) with little success (three W. virgo). From there we drove to our overnight destination of Cobar (which, we discovered, has a pretty good Thai restaurant!).

Day three – Cobar to Hillston

Anwar has been digitising the field notebooks of Ken Key for his PhD and one of these was a trip Key and White did to a place near Hillston where White and his family had discovered W. virgo the year before. Key and White’s trip was almost at exactly the same time as ours but 57 years earlier (17^th to 20^th February, 1962). They stopped at a few other sites as well so we decided to revisit some and see how things had changed.

The first site was a patch of mallee that Key and White camped in at what is now Nombinnie Nature Reserve. They found 15 species of grasshopper but we only found two – the matchstick grasshopper Capsigera P51a and another unnamed grasshopper Macrotona sp. 19. The latter is quite a beautiful species that is closely associated with Triodia and dives into it to hide.

The second site was a few kilometers further down the road, and was again mallee but with some green vegetation by the roadside. We did much better here, finding around six species. Key and White found seven species here in 1962, but not all the same ones. One species that we did find in common was the Halgania grasshopper Histrioacrida roseipennis which is thought to be a specialist of the Halgania plant.

One we didn’t find in common with Key and White was the Crested Tooth Grinder Ecphantus quadrilobus – named for the noise it makes when disturbed (we didn’t hear the one we found make the noise). We also found a couple of Australian Plague Locusts Chortoicetes terminifera, which have been keeping a low profile since 2011 when the last big plagues occurred.

A third site of Key and White’s we visited was a grassy roadside habitat just north of Hillston with clay soil, and there were grasshoppers everywhere! They were very hard to catch but we did see a lot of Macrotona securiformis as well as the beautiful Stropis maculosa, Goniaea sp., a Peakesia sp. and lots of Acrida conica – none of these species were recorded by Key and White but we did find Oedaleus australis in common.

Finally, we revisited the site where W. virgo was first discovered, 14 km WNW of Monia Gap near Hillston. In 1962 Key and White found 24 species of grasshopper here whereas we found 11 species. Despite about 4 hours of searching we only found 3 W. virgo. The population here seems to have crashed compared to previous years.

We were excited to find three early instar Keyacris P108a, an inland version of the more well known (and now threatened in Victoria) Keyacris scurra. I found the latter species as 2^nd instar nymphs in late January in Canberra this year. The Keyacris species at the Monia Gap site thus appear to have a similar life cycle but are a little behind. Key and White reported that they found nymphs at the same time of year in 1962 but didn’t say what instar. There appeared to be little to eat for this tiny grasshopper  but there were a few sorry-looking daisies about. We think they must really be looking forward to some autumn rain.

Day four – Cobar to Melbourne

Anwar was glad to see the back of the flies! Vanessa and Anwar (on their first real grasshopper field trip) were surprised by the diversity shown by Warramaba virgo in host plant preference and were a little annoyed that at some sites Capsigera suddenly presented some green colour morphs that were mistaken to be the highly sought after W. virgo until they got the hang of the morphological differences (such as more bulbous eyes). But overall it was a successful trip and hopefully will lead to more insights into how parthenogenesis evolved and spread in Warramaba virgo.

Written by Michael Kearney with the assistance of Vanessa White and Anwar Hossain