I caught this Cuckoo wasp (Chrysididae spp.) sneaking into a newly made mud dauber nest just after the builder in the previous photo left for another load of mud (note the darker, wet mud). This pretty, metallic green wasp will lay her egg in the nest. Her larvae will eat the spiders which were to be the "baby food" for the mud dauber larvae and then those larvae will be eaten by the parasitic cuckoo wasp larvae. Unlike the cuckoo birds which are often much larger than their unwilling host parents, these wasps are much smaller than the wasps they parasitize.