Polistinae of south-eastern Australia
Workbook
Responding to a prompt from a fellow iNaturalist contributor, I’ve been taking a closer look at paper wasps of south-eastern Australia. Can we reliably separate species from field photos? And specifically, are the Ropalidia sightings south of around Port Macquarie (latitude ~32ºS) being correctly identified? Might the common, tropical species R. revolutionalis be moving south … or are sightings of R. plebeiana (widespread in the south-east) simply being mistaken for R. revolutionalis?
The Polistinae are largely tropical in distribution. Only a handful of species are known from NSW, with even fewer from the southern parts of the state. So perhaps a doable project, and certainly worth a shot.
INTRODUCTION : list of Australian species in the subfamily Polistinae; schematic showing how to distinguish Ropalidia from Polistes; annotated figures showing morphological structures and the terms used.
PART ONE - Ropalidia: summary descriptions (matrix) for the six species known to occur in south-eastern Australia; field photos examples (linked to iNaturalist observations); structural differences between three otherwise similar-looking species; field photos of nests.
PART TWO - Polistes: summary descriptions (matrix) for the five species known to occur in south-eastern Australia; field photos examples (linked to iNaturalist observations).
END NOTES: limitations of distribution data; extracts and images published elsewhere (e.g. museums; BOLD); reference list.
INTRODUCTION
Ropalidia and Polistes of Australia
Polistinae is a subfamily of Vespidae and in Australia includes just two genera: Ropalidia and Polistes. The only other social wasps in Australia are the introduced Vespula (subfamily Vespinae), which includes the locally notorious ‘European Wasp’, Vespula germanica.
There are currently 34 Australian species of Polistinae listed on AFD. The most recently described species are attributed to the major review of Australian social wasps undertaken by O.W. Richards (1978). Much of what I’ve summarised below is based on that publication.
The highest species diversity is found in Queensland, the Northern Territory, and northern Western Australia. According to Richards (1978), Ropalidia plebeiana “seems to be the only common Ropalidia in south-eastern Australia” (p. 79). The Polistes fauna is similarly depauperate in the south. The widespread Polistes humilis is perhaps the most commonly sighted of the five species known to occur south of the QLD-NSW border.
PART ONE
Southern Ropalidia species
The table below lists some of the characters for each of the species known from NSW or further south. The emphasis is on features that might be visible in field photos.
Click image to open/download latest version as pdf (<200kb)
A few examples from iNaturalist
These images illustrate some of the identifying features. They may assist in ‘photo matching’, but it is advisable to refer also to the matrix above.
When colour alone is not enough
The striking … and strikingly distinctive! …. colour patterns of R. romandi, R. socialistica, and R. impetuosa are often all that is needed for a convincing ID. The same cannot be said for the remaining three southern candidate species. R. plebeiana, R. revolutionalis and R. gracilenta are all dark coloured wasps, with more limited and variable yellow markings. For these species, differences in body shape and nest structure provide key clues to identity.
The shape of the first two metasomal segments is distinctive in R. gracilenta. It also differs between R. plebeiana and R. revolutionalis, although the distinction is not quite so obvious. [refer Figures 15-22 in Richards (1978), extract included in the ‘Bits & pieces’ section at the end of this page.]
A second structural clue is the shape of the pronotal keel, laterally. Is it high, sharp and angled (R. plebeiana), sinuous (R. revolutionalis), or smoothly curving and long (R. gracilenta).
Refer to the summary table above for details.
Nest architecture
Polistinae are eusocial wasps. There is a usually only one actively reproductive female at any one time, although this varies and some species regularly include multiple such ‘queens’ or ‘gynes’. The workers are female and are largely indistinguishable from the gynes. Colony members share in nest construction, and in the care and feeding of the young.
The size, shape, and location of the nest varies between species. It is particularly helpful for distinguishing between Ropalidia species of temperate Australia.
Refer to the summary table above for details.
Female or male?
The sex differences within the Ropalidia species above are comparatively slight. Males are generally similar to females in body colour and structure … but with some differences. Males often have more extensive yellow markings on the face and underside of the thoracic segments (‘sternites’). Blackened areas may be more extensive. The antennae may be modified, and the gastral segments differ in their proportions.
So before colour-matching a wasp to determine its species ID, it is helpful to check its sex.
Fortunately, when comes to differentiating males and females, there are two reliable differences that are useful for field photos: the number of antennal segments, and the number of visible metasomal tergites.
Adult males observed at nests are almost certainly on the lookout for emergent females with which to mate.
PART TWO
Southern Polistes species
The table below lists some of the characters for each of the Australian species known from NSW or further south. The emphasis is on features that might be visible in field photos.
Click image to open/download latest version as pdf (<200kb)
A few examples from iNaturalist
These images illustrate some of the identifying features. They may assist in ‘photo matching’, but it is advisable to refer also to the matrix above.
I have also included images of two (sadly) common, introduced species of Polistes. Just for reference. Neither could be mistaken for any of the locals.
Variation and uncertainty
While many iNaturalist images neatly match a single species description, others are proving more of a challenge. In particular, distinguishing between P. humilis synoecus and some colour variants of P. stigma townsvillensis is not trivial. Forewing markings can help, if they show clearly in the photos. I’ve yet to find a consistent structural difference that might be useful for field photos. Hopefully, the situation will clarify over time. With practice.
For now, I’ll rely on published distribution data. Richards (1978) states that the most southern collection site for P. humilis synoecus was Abernethy (32º54’S).
END NOTES
A cautionary note re distribution data
It is important to remember that published location data is an imperfect measure of a species’ range. Such collection data simply tells you where a species has been found, at some time in the past. Not all areas of the country are sampled evenly. Far from it! And species distributions can change with time.
With this in mind, I’ve taken a conservative approach in compiling a list of candidate southern species. Based on Richards (NSW) large scale revision, I’ve included all species collected from anywhere south of the NSW-QLD border in eastern Australia. Included are any species with a listing in NSW, Victoria, SA and Tasmania. I excluded those known only from QLD, NT, WA.
It is quite likely that this list will be incomplete for northern NSW. Species well-known around highly populated regions in south-eastern QLD often go undetected in nature reserves and rural areas just south of the border.
So I advise caution when using the above notes and matrices to identify paper wasp sightings north of, say, Port Macquarie. If a good match cannot be found in the matrix, it may well be an unlisted ‘QLD’ species.
From Port Macquarie, south, the list should hold up quite well. Indeed, a more recent review of Ropalidia distribution records for temperate Australia (Sait & Kojima, 2005) found that R. plebeiana is the only Ropalidia found south of latitude -30ºS.
Bits & pieces
References
Carpenter, J.M. & Brown, G.R. 2022. Catalogue of the Australian social wasps (Hymenoptera: Vespidae). Zootaxa 5214(4): 451–495
Hook, A.W. & Evans, H.E. 1982. Observations on the nesting behaviour of three species of Ropalidia Guérin-Méneville (Hymenoptera: Vespidae). Journal of Australian Entomological Society, 21: 271-272
Itô, Y. & Higashi, S. 1987. Spring Behaviour of Ropalidia plebeiana (Hymenoptera: Vespidae) within a huge aggregation of nests. Applied Entomology & Zoology, 22(4): 519-527
Kojima, J. 1993. Feeding of larvae by males of an Australian Paper Wasp, Ropalidia plebeiana Richards (Hymenoptera, Vespidae). Japanese Journal of Entomology 61 (2): 213-215
Richards, O.W. 1978. The Australian social wasps (Hymenoptera: Vespidae). Australian Journal of Zoology Supplementary Series 61: 1-132
Saito, F. & Kojima, J. 2005. Colony cycle in the south-eastern populations of Ropalidia plebeiana, the only Ropalidia wasp occurring in temperate Australia. Entomological Science 8: 263-275
This is a workbook page … a part of our website where we record the observations and references used in making species identifications. The notes will not necessarily be complete. They are a record for our own use, but we are happy to share this information with others.