Well, a flash of memory last night just after I switched off the computer, and snail's gentle nudge in the comment on yesterday's post reminded me that I know perfectly well that my mud daubers must be Sphecid wasps.
They are more commonly called sand wasps, which is an awfully confusing and misleading name, many wasps in the family Sphecidae are mud daubers, dabbers, brickies and general pottery experts.
Individual species specialise in specific types of prey - so it's likely that this locally common dauber specialises in crab spiders, as she is quite a smallish wasp. Spiders are a great deal more abundant here than Lepidopteran larvae (due in no small part in my opinion to the overabundance of exotic pest paperwasps, Polistes sp).
Perhaps due to the abundance of baby food, the spider-specialty daubers are en masse on the farm - in every nook, cranny and crevice. Stand too still for too long and they will investigate any available orifice for nursery sites. Earholes are favoured.
They use driza-bones, boots, car engines, tools, tractor seats, garden gloves and probably more naturally occurring sites too (but I haven't seen that - maybe like swallows they have abandoned the natural for the much more convenient and abundant anthropogenic). Just like the Megachilid bees.
Which reminds me of another reason to love Sphecids - bees are commonly referred to as sphecoid like, and are believed to have derived from Sphecids. In effect, just Sphecids that provision their nurseries with pollen and nectar rather than arthropods.
But custom hasn't staled their infinity variety for me, and I never tire of their ingenious and often decorative creations. (A more tidy hausfrau than I could be driven into a cadenza. There's a nice thought).