Seasonal changes start early in the forest. In the chill of mid August, stands of heathy shrubs suddenly bloom white. On clear, sunny days their vanilla fragrance heralds the approach of spring … and the return of the bees. Then, within a month, insects of all kinds are making an appearance.
Some I know well, others not at all.

My early season highlights

First, the bees

So many flies

… including many that are new for our home list. Several are rare records for iNaturalist too!
The order Diptera – the flies – is a hugely speciose group. In terms of numbers of species and absolute abundance, they outrank other megadiverse groups such as beetles, wasps and moths (Marshall, 2012, p. 15). So as I wander the forest in early spring, I should not be surprised that such a wide variety of flies are on the wing. Nonetheless, the appearance of four different species of bee flies, across three genera, on a single day does seem exceptional!

And then there’s everything else

Just a small taste of what is yet to come.

We’re on the cusp of the great spring explosion in insect numbers and diversity. Every day now, new species of bees, dragonflies and wasps make their debut appearance. The pace of forest life is rapidly accelerating – and I’m soon to be very, very busy!

Three projects on the go

Despite this being the first blog post I’ve published in months, my naturalist activities have continued without pause. Here’s a quick summary of the latest projects. All are ongoing. And yes, they all involve wasps.

1. PROJECT Rhopalum

Rhopalum coriolum (CRABRONIDAE: Crabroninae) – a manuscript in preparation.

We first discovered these little-known wasps nesting here last year. After working through their identification we realised there’s an important story to tell. Nothing has previously been published on their biology, which is quite different to most Rhopalum species.

So we are preparing a paper which we’ll submit to a refereed scientific journal. I wrote a Rhopalum blog in September 2022 (Nesting habits of a little-known wasp) but we also want to ensure that the knowledge is not lost when, at some future time, our website ceases to be.

This year we collected data from a second breeding season. The females reappeared on cue in late August. For a month the nesting ground was busy as they stocked their burrows with paralysed flies. We timed their comings and goings for many hours across those four weeks – rather a lot of time to spend staring at one patch of dirt, not daring to look away lest we miss the action. So now it’s back to writing up our findings.

2. PROJECT Cerceris

Cerceris antipodes (CRABRONIDAE: Philanthinae) – ongoing study of their nesting behaviour.

This year I view these little wasps with greater awareness of their individual life histories. Having observed them closely during the 2022-23 season, and read the research publications of David B. McCorquodale from the late 1980s, I can now better interpret their behaviours. For the full story, see my July blog post Cerceris: an almost-social wasp.

On recent warm October days, traffic across the nesting ground has been non-stop. There are dozens of active burrows, with females having regular success in their search for beetle prey to feed their larvae. But they don’t have it all their own way … they face trials and tribulations aplenty.

3. PROJECT Braconinae

Callibracon and related wasps (BRACONIDAE: Braconinae) – my first exploration of this taxon.

I was wandering about one sunny morning in mid September, simply enjoying the bush, when these colourful little wasps caught my eye. They were circling low over a flat patch of ground. The sandy soil was largely bare, with just a few struggling grasses and scattered leaf litter. So began Project Braconinae.

This was a species I’d never seen before. I was instantly intrigued. And then I spotted them plunging their ovipositors down in between the coarse grains of sand! Now I was hooked. Who are they and what are they up to?

They were clearly choosing concealed targets, not simply dropping eggs at random. For example the six images above show the actions of one female, taken over 4 minutes. Between each pair of shots she flew or stepped away, only to return and probe the exact same location.

Their numbers continued to grow. Four weeks on, and they’re still around.

I found similar-looking wasps on iNaturalist, but their identifications were largely uncertain. My wasps looked like Braconinae, but which genus? Most colourful, shiny braconines are labelled Callibracon, yet Australia has many other genera in that subfamily. Perhaps if I could confirm the wasps’ identity – at least to genus – I might learn the identity of the subterranean targets for their eggs.

Project Braconinae is still at an early stage, but already I have some results. For example, I now have a confirmed ID for the wasps above – genus Vipiellus.

My next step is to become more familiar with other braconine genera. I collected a couple of the small, dark-winged braconines we commonly see flying around forest vegetation. And after a bit of work I now have a name for them too … Pycnobraconoides.

Most recently, I’m pleased to say, I collected a ‘true’ Callibracon. So now I have a baseline reference, an example of that widespread and common genus in the hand, for comparison with other sightings.

I’ll tell the story in more detail in a later blog post. For now, here are a few close-ups. The images highlight some of the features that help to distinguish the various genera. Plus I think they are all beautiful, in their own way. Even in death.

For anyone interested in the full details, here are links to my working notes pages for each: Vipiellus; Pycnobraconoides; Callibracon.

References

Blackall, A.G., Mackay, D.A. & Whalen, M.A. 2023. Impact of reserve area on reproduction of a moth-pollinated Stackhousia Sm. (Celastraceae) species in a fragmented landscape. Austral Ecology, 2023; 00: 1-23.

Evans, H.E. & Hook, A.W. 1986. Prey selection by Australian wasps of the genus Cerceris (Hymenoptera, Sphecidae). Journal of Natural History, 20(6): 1297-1307.

Hawkeswood, T.J. 1994. Review of the biology and host plants of Australian Chrysomelidae (Coleoptera) associated with Acacia (Mimosaceae). Chapter in Novel Aspects of the Biology of Chrysomelidae. Series Entomologica, 50: 191-204. available from author on ResearchGate (link)

Houston, T. 2018. A Guide to Native Bees of Australia. CSIRO Publishing, Clayton South, Vic.

Marshall, S.A. 2012. Flies: The Natural History and Diversity of Diptera. Firefly Books Ltd, New York.

Parslow, B.A., Schwarz, M.P. & Stevens, M.I. 2020. Review of the biology and host associations of the wasp genus Gasteruption (Evanioidea: Gasteruptiidae). Zoological Journal of the Linnean Society, 189: 1105-1122 (open access)