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Psyche 
[Vol. 92 
egg she lays in each brood cell. Most species dig holes in the ground, 
but some nest in pre-existing cavities whereas others construct mud 
nests. Regardless of the type of nest, all species of sphecids show 
some sort of final nest closure. This nearly always includes behavior 
that apparently compacts or settles the material used. Most sphecids 
and pompilids (spider wasps) pack the soil by repeatedly tapping or 
pounding on the substrate with the last abdominal segment (Car- 
penter, 1930; Evans, 1966b), often while simultaneously vibrating 
the abdomen (Endo, 1981). However, one subfamily of sphecids, the 
Sphecinae, differs in that they tamp or press the soil with the front 
of the head. It is in this group that tool-using behavior has evolved. 
In this paper I examine the frequency, origin and adaptive value of 
tool using in the Sphecinae. 
Throughout the following discussion of nest closure in the Sphe- 
cinae, I include observations I have made on various species. De- 
scriptions of Sphex ichneumoneus come from notes, slides and films 
taken during a five-summer study (July- August) at sites in Dear- 
born, MI (1972-75, an aggregation of 73 individually marked wasps 
was observed completing 200 final closures over the four years), 
Exeter, NH (1975, 33 wasps and 60 permanent closures) and North- 
field, MN (1976, 136 wasps and 150 closures) (see Brockmann 1979 
and Brockmann and Dawkins 1979 for further details). The great 
black wasp, Sphex pensylvanicus, was observed in 1974 (25 Aug- 
16 Sep) at a gravel pit near Rensselaerville, NY (25 individually 
marked wasps and 12 final closures were observed). Brief observa- 
tions of Ammophila urnaria were made at the same site (3 wasps, 2 
nest closures). One observation of nest closing was made on Poda- 
lonia pubescens, Ammophila wrightii and A. breviceps near the 
Southwestern Research Station, Portal, AZ (30 May-22 June 1975). 
Ammophila aberti was observed briefly at Chaco Canyon National 
Monument (10 wasps seen, one nest closure, 30 June 1975). Brief 
observations on A. aureonotata and A. pictipennis were made at the 
Archbold Biological Station, Lake Placid, FL (14-17 April 1974). 
Nest Closure 
The ground-nesting Sphecinae generally construct a simple nest: a 
long, straight, main-tunnel with a perpendicular side-tunnel and ter- 
minal brood chamber. They dig the nest by biting at the substrate 
and scraping away the loosened soil with rakes on their front tarsi 
