Bembix (BEMBICINAE: Bembicini)
Workbook
Bembix is one of the largest of the crabronid genera, worldwide. The genus is represented on all continents (bar Antarctica) and Australia is particularly species rich. There are currently 84 Australian species listed on AFD: as large as 24mm, as small as 8mm; brightly patterned in yellow or white, a mixture, or sometimes almost entirely black.
Bembix are also among the most familiar – and photographed - of the crabronids. Yet despite the large number of images online, rarely are these identified to species level. I hope to be able to put names to at least some of them. Soon.
Evans & Matthews (1973) provide a way forward
Thanks largely to the extraordinary efforts of Howard E. Evans and Robert W. Matthews, the taxonomic and biological diversity of Australian Bembix is well documented. Of particular importance is their 1973 publication Systematics and Nesting Behavior of Australian Bembix Sand Wasps. However, to the best of my knowledge, this impressive monograph is not available online. I feel very fortunate to have been gifted a copy of the book (all 387 printed pages) by one of the authors, Robert W. Matthews. This book includes the original description of 55 species, and reviews all those previously described. Since that time, a further four species have been added … again, thanks to the work of Howard E. Evans (1982, 1990).
Although the authors stress that their 1973 book is “far from being a definitive monograph of the Australian Bembix” (p. 1), it is an absolute gem. It is the culmination of twelve months of fieldwork (1969, 1970 & 1972), travelling throughout Australia, collecting and studying the nesting behaviour of sand wasps. Importantly, the authors also made an exhaustive study of material held in collections:
“This led us to study the Bembix in all major museums known to contain Australian material and to study the types of all species described from that continent (except two which are evidently lost).” (p.1).
As part of my own, modest crabronid project, I have recently turned my attention to Bembix. With ‘the good book’ in one hand and iNaturalist images in the other, I am seeking a way to put species names to faces.
Is it possible to confidently recognise individual species from field photos? If so, which species? And what features are diagnostically most useful?
There are currently nearly 1600 sightings of Australian Bembix on iNaturalist, and just a few of these have reliable species level identifications. Can I improve on this? Only time will tell – but I am optimistic.
Morphology
Australian Bembix can be distinguished from other members of the subfamily by the following shared characters: labrum exserted and at least as long as broad (in some cases, the length is twice the width); eyes essentially parallel; vertex sharply depressed alongside the eyes; ocelli greatly reduced, virtually absent. In addition, the gaster is sessile, with T1 nearly as broad as T2.
In distinguishing between species, useful characters include: labrum shape & colour; clypeus shape & colour; frons width and markings; front basitarsus shape and spination; male sternite shape; colour and dorsal patterning of the mesosoma and metasoma. For further details, see pages 9 to 11 of the Evans & Matthews (1973), below.
The images below illustrate many of these structural features and colour patterns, as discernible in field photos.
Bembix of Eastern Australia
A first step
Half of Australia’s described Bembix species have been collected in the eastern part of Australia, and it is these that I am concentrating on in the first instance. This makes the task more manageable. It is also where the majority of iNaturalist sightings were made (83%, at last count). In addition, it is where I live and spend most of my time – so that lends its own bias to my decision. I do plan to cast an eye further west eventually. But one step at a time.
So for now, the table below contains only species known to occur in QLD, NSW, ACT, Victoria, Tasmania, or south eastern SA. Not included are species known only from WA, NT or SA outside the south east.
Summary table, with emphasis on the more common species
The following summary table for eastern species is large and detailed. Necessarily so. With 44 known species, and so much recognised variation within species, a more simplified cheat sheet would not really work. In nearly every case, a range of structural and colour features will need to be considered in combination, and the options available will always be constrained by what details are visible in any given set of photos.
Perhaps over time I will delete some of the columns, but for now I’m being as thorough as possible.
click image to download latest version as pdf (1.3MB)
Some of the more recognisable species
Some good news. It is indeed possible to confidently ID several Australian Bembix species from field photos, despite the large number of species and the intraspecific variation of many. Here are a few examples.
Please note. The above identifications are simply my suggestions, based solely on comparing the images to the published descriptions. This is not intended as a definitive photo guide. The images are all linked to the source iNaturalist observations, and these should be checked for corrections and comments over time. As the iNaturalist community starts taking these wasps to species level, I’m sure we will all hone our identification skills.
Essential extracts
Diagrams in Evans & Matthews (1973) show various details referred to in the species descriptions, such as:
the front tarsi, including basitarsi and pecten spines (males & females; many species)
the mid tibia, including tibial spurs (males & females; many species)
male antennae (most species)
The relevant figures are referenced in my summary table (matrix), and copies of the figures are included below.
Also included are pages 3 to 8, presenting a summary of their major conclusions.
Evans and Matthews: dedicated students of comparative behaviour
“There are fragmentary reports that some of the southern hemisphere species have unusual prey preferences (Wheeler and Dow, 1933). Clearly it is time that students of comparative behavior turned their attention to the many species of this relatively well-studied genus occurring south of the equator. [] … We quickly found that no comparative behavioral studies were possible without first clarifying the systematics of the Australian Bembix. In fact, accurate identification of species proved almost impossible, and about a third of the species we studied in the field we found to be undescribed.” (Evans & Matthews, 1973 p.1)
As nesting behaviour of sand wasps was the real motivation behind their study, it seems only fitting that I include at least some of their ethological findings. I have added brief notes and examples to my summary table. The authors’ own Summary of Major Conclusions (pp 2-7, see above) includes several findings related to behaviour. In addition, below are pages dealing with the brood nest digging behaviour of both B. variabilis and B. littoralis. I feature these particular species for two reasons. First, they are two of the most abundant and widely distributed species of the genus. Second, females are very difficult to tell apart in the field: “We have found that it is often easier to tell these two species apart by the structure of the nests than by the structure and coloration of the adult females.” (Evans & Matthews, 1973. p 292).
Key to Species
Of course, Evans & Matthews (1973) includes a key to all 80 species known at that time.
Other bits & pieces
Many species are represented in Australian museum collections, but few of these are as yet available as online images. Below are those I’ve found to date, including the holotype of Bembix wanna from Victoria. BOLD has 10 specimens listed, and the genetics suggest these represent at least six different species, but they are identified to genus only and with just a single, lateral image of each. I have included a couple here, simply to illustrate structural and colour diversity.
References
Evans, H.E., Evans, M.A. & Hook, A. 1982. Observations on the nests and prey of Australian Bembix sand wasps (Hymenoptera: Sphecidae). Australian Journal of Zoology 30: 71-80
Evans, H.E. & Matthews, R.W. 1973. Systematics and Nesting Behavior of Australian Bembix Sand Wasps. Memoirs of the American Entomological Institute, Number 20.
Evans, H.E. & Matthews, R.W. 1975. The sand wasps of Australia. Scientific American, 233(6); pp 108-115
Evans, H.E. 1982. Two new species of Australian Bembix sand wasps, with notes on other species of the genus (Hymenoptera, Sphecidae). Australian Entomological Magazine 9: 7-12
Evans, H.E. 1990. New Australian species and records of the promontorii group of the genus Bembix F. (Hymenoptera: Sphecidae: Nyssoninae). Journal of the Australian Entomological Society 29: 27-30
Evans, H.E. & O’Neill, K.M. 2007. The Sand Wasps: Natural History and Behaviour. Harvard University Press
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.