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The Sphecidae are a cosmopolitan family of wasps that includes digger wasps, mud daubers, and other familiar types that all fall under the category of thread-waisted wasps. Both of the traditional definitions of the Sphecidae (the conservative one, where all the sphecoid wasps other than ampulicids and heterogynaids were in a single large family, and the more refined one, where the seven large sphecid subfamilies were each elevated to family rank) have recently been shown to be paraphyletic, and the most recent classification is closer to the conservative scheme; the families Heterogynaidae and Ampulicidae are the sister taxa to what are now two families (instead of one), the Sphecidae and Crabronidae. Thus, the bulk of the sphecoid wasps are now placed in Crabronidae, and the Sphecidae per se are much more restricted in concept, equivalent to what used to be the subfamily Sphecinae.
The biology of the Sphecidae, even under the restricted definition, is still fairly diverse; some sceliphrines even display rudimentary forms of sociality, and some sphecines rear multiple larvae in a single large brood cell. Many nest in pre-existing cavities, or dig simple burrows in the soil, but some species construct free-standing nests of mud and even (in one genus) resin. All are predatory, but the type of prey ranges from spiders to various dictyopterans or orthopteroids to caterpillars (of either Lepidoptera or other Hymenoptera); the vast majority practice mass provisioning, providing all the prey items prior to laying the egg.
Goulet, H., Huber, J.T. (1993) Hymenoptera of the World. Agriculture Canada Research Branch, publication 1894/E. 668pp.