Sometimes looking these things up really deflates my belief that I have some knowledge of the natural world!! And I always wish I paid more attention to the creatures and got right up looking at them, taking notes, while I shot the photo!
So, the Australian Museum has a lot of information on wasps, which you can find here, and then finishes with this (and that's where all my doubts come from):
"What looks similar?
- Bees are closely related to wasps and share many features. In general the following features distinguish bees from wasps: legs and body hairy with forked hairs; hindlegs enlarged to form baskets of hairs to carry pollen; wings have cells; movement generally restricted to interaction with flowers and returning to nests.
- Ants are closely related to wasps and share many features. To further complicate matters some wasps look and behave remarkably like certain ant species. In general the following features distinguish ants: constricted 'waist' with one or two knobs; antennal segment closest to body very long (five times as long at least) to any of the remaining segments; presence of certain glands (microscope and taxonomic expertise required). Wasps never have all of these features.
- Sawflies are closely related to wasps and share many features. Sawflies can be distinguished by a lack of constriction at the 'waist' and more complete wing venation. The wings have more veins and cross-veins that form cells, with at least one vein extending to wing margin. They are nearly always plant feeders (one or two are parasites of wood-boring beetles), and females have a saw-like ovipositor folded into a groove when not in use.
- Some moth families are wasp-like in appearance. Some species of case moths (Family Psychidae), cup moths (Family Limacodidae), clearwing moths (Family Sesiidae), forester moths (Family Zygaenidae), and hawk moths (Family Sphingidae) have adults which have clear membranes on their wings, with scaling restricted to veins and the body of the moth. This can sometimes give a wasp-like appearance (eg. Family Sesiidae), and may result in incorrect identifications. The scales on the body should still identify these insects as moths."