PEMPHREDONINAE
Workbook
[ Cover image: Stephen Fricker (shared CC BY), inaturalist record 104798102 near Adelaide]
Soon to be recognised as a family, this group has long been considered part of the Crabronidae … and so it has been one of my target taxa of interest. Many of its members are small, and therefore often overlooked by field naturalists. That is my justification for delaying closer investigation … until now.
Recognising Pemphredoninae
In general terms, these wasps can be recognised by the following combination of features.
small size
cuboidal head
very short clypeus
eyes entire (not notched), widely separated, and essentially parallel
normal ocelli
typically 2 submarginal cells & an enlarged stigma (with a few exceptions).
Distinguishing between genera
There are just 7 genera of Pemphredoninae in Australia. Psenulus is quite distinct, and under taxonomic changes proposed by Sann et al. (2018), it will move to an entirely separate family. Among the remaining six (tribe Pemphredonini), Arpactophilus dominates in terms of species numbers.
Click image to open or download as pdf (<400kb)
Gaster shape
The first step involved in distinguishing between genera is the shape of the gaster – petiolate or sessile. This is not a perfect in terms of diagnosis, but it’s a good start. For example, a sessile gaster will almost certainly be either Arpactophilus or Spilomena.
Head architecture
The presence or absence of features such as the occipital carina, scapal basin, and frontal carina are also diagnostically valuable – most particularly in distinguishing Arpactophilus from Spilomena. Despite their small size, it is often possible to make out these details … if you know where to look.
A few examples
The following images from iNaturalist illustrate several of the various features used in distinguishing between genera.
Bits & pieces
Various extracts from the literature.
Select species, in detail
As opportunities arise, I take a closer look at individual species within this subfamily.
References
Bohart, R.M. & Menke, A.S. 1976. Sphecid Wasps of the World: A generic revision. University of California Press.
Matthews, R.W. & Naumann, I.D. 2002. Descriptions and biology of nine new species of Arpactophilus (Hymenoptera: Crabronidae), with a key to described Australian species. Journal of Hymenopteran Research 11(1): 101-133 freely available from BHL
Finnamore, A.T. 1995. Revision of the world genera of the subtribe Stigmina (Hymenoptera: Apoidea: Sphecidae: Pemphredoninae), Part 1. Journal of Hymenopteran Research 4: 204-284
Melo, G.A.R. & Naumann, I. 1999. Two new genera of pemphredonine wasps from Australia (Hymenoptera: Apoidea, Crabronidae). University of Kansas Natural History Museum Special Publication 24: 221-229 freely available from BHL
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.