Belongs within: Bembicidae.
Sphecius, cicada killers, is a cosmopolitan genus of large ground-nesting wasps of which the North American species S. speciosus is known to provision its nests with cicadas of the genus Tibicen (Bohart & Menke 1976).
Characters (from Bohart & Menke 1976): Large wasps, some attaining a length of more than 35 mm; inner eye margins converging slightly to strongly below; mandible with an inner subtooth; labrum prominent, exposed part often half as long as broad; antenna long, gradually enlarged toward apex but not obviously clubbed, last four articles in male not specially modified in contrast to other articles; impressed median line on frons often weak or incomplete; pronotal collar thin and closely appressed to scutum; female foretarsal rake weakly developed, fore basitarsus with three or more stout setae before apex; female arolia about equal in size; posterolateral oblique scutal carina present; prescutellar sulcus foveate: episternal-scrobal sulcus curved backward around hypoepimeron, scrobal sulcus not continued forward toward omaulus which is distinct; sternaulus absent; acetabular carina present in Palaearctic species; metapleuron gradually or hardly narrowed below; scutellum overlapping metanotum; fore wing with media diverging before cu-a; stigma unusually small; veinlet of submarginal cell II between recurrents short; hindwing media diverging well before cu-a, jugal lobe considerably larger than tegula; midtibia with two apical spurs; propodeal enclosure large, extensively vertical as well as horizontal; no spiracular groove; metasoma stout, tergum I broad; male with seven terga normally visible, sterna without fimbriae, sternum VIII sting-like or sword-shaped; female pygidial plate flat, sharply margined, closely punctate.
<==Sphecius Dahlbom 1843C85
| i. s.: S. lutescens (Radoszkowski 1877)NP09
|--S. (Sphecius) [incl. Hogardia Lepeletier 1845]BM76
| |--S. (S.) speciosus (Drury 1773) (see below for synonymy)BM76
| |--S. (S.) convallis Patton 1879 [incl. S. raptor Handlirsch 1889]BM76
| |--S. (S.) grandis (Say 1823) [=Stizus grandis; incl. St. fervidus Cresson 1872, St. nevadensis Cresson 1874]BM76
| |--S. (S.) hogardii (Latreille 1809) [=Stizus hogardii; incl. *Hogardia rufescens Lepeletier 1845]BM76
| | |--S. h. hogardiiBM76
| | `--S. h. bahamas Krombein 1875BM76
| `--S. (S.) spectabilis (Taschenberg 1875) [=Stizus spectabilis]BM76
| |--S. s. spectabilisBM76
| `--S. s. nobilis Brèthes 1910BM76
|--S. (Nothosphecius Pate 1936)C85
| |--S. (*N.) grandidieri Saussure 1887C85 [=Stizus grandidieriBM76; incl. Sp. freyi Handlirsch 1892BM76]
| |--S. (N.) citrinus Arnold 1929BM76
| |--S. (N.) malayanus Handlirsch 1895BM76
| |--S. (N.) milleri Turner 1915BM76
| | |--S. m. milleriBM76
| | `--S. m. aurantiacus Arnold 1940BM76
| `--S. (N.) pectoralis (Smith 1856) [=Stizus pectoralis]C85
`--S. (Sphecienus Patton 1879)BM76
|--S. (*S.) nigricornis (Dufour 1838) [=Stizus nigricornis]BM76
|--S. (S.) antennatus (Klug 1845) [=Larra antennata; incl. Stizus aberrans Eversmann 1849]BM76
| |--S. a. antennatusBM76
| `--S. a. impressus Kokujev 1910BM76
|--S. (S.) claripennis Morice 1911BM76
|--S. (S.) conicus (Germar 1817) [=Stizus conicus; incl. St. luniger Eversmann 1849]BM76
| |--S. c. conicusBM76
| |--S. c. creticus Beaumont 1965BM76
| `--S. c. syriacus (Klug 1845) [=Larra syriaca]BM76
|--S. (S.) hemixanthopterus Morice 1911BM76
|--S. (S.) intermedius Handlirsch 1895BM76
|--S. (S.) nigricornis (Dufour 1838) [=Stizus nigricornis]BM76
|--S. (S.) percussor Handlirsch 1889BM76
|--S. (S.) persa Gussakovskij 1934BM76
|--S. (S.) schulthessi Roth 1951BM76
|--S. (S.) turanicus Roth 1959BM76
`--S. (S.) uljanini (Radoszkowski 1877) [=Stizus uljanini; incl. St. terminus Kirby 1889]BM76
Sphecius (Sphecius) speciosus (Drury 1773) [=Sphex speciosus; incl. *Sphecius speciosus Dahlbom 1843 non Sphex speciosus Drury 1773, Vespa tricincta Fabricius 1775, Stizus vespiformis Latreille 1818 non Sphex vespiformis Fabricius 1775]BM76
*Type species of generic name indicated
References
[BM76] Bohart, R. M., & A. S. Menke. 1976. Sphecid Wasps of the World. University of California Press: Berkeley.
[C85] Cardale, J. C. 1985. Vespoidea and Sphecoidea. In: Walton, D. W. (ed.) Zoological Catalogue of Australia vol. 2. Hymenoptera: Formicoidea, Vespoidea and Sphecoidea pp. 150–303. Australian Government Publishing Service: Canberra.
[NP09] Nemkov, P. G., & W. J. Pulawski. 2009. A cladistic analysis of Gorytina (Hymenoptera: Crabronidae: Bembicini), with a reclassification of the subtribe. Zootaxa 2069: 1–17.