1985] 
Brockmann — Digger wasps 
317 
Fig. 3. S. ichneumoneus packing soil. After a bout of 5-15 seconds of scraping, 
the wasp enters her nest and packs the soil. She applies the open mandibles and oral 
surface of the head to the substrate and presses down for one half to two seconds, 
vibrating her head and body intensely. She occasionally raises one or both hind legs 
above the substrate. After 5-20 sec of packing she then reemerges at the surface for 
another bout of scraping. Late in the filling process, when the nest fill is within 1 cm 
of the surface, the wasp engages in particularly intense and prolonged packing. In 
addition to pressing on the fill, she also picks up stones, sticks, clods of dirt, or other 
pieces of debris, carries it to the nest in her mandibles and presses it down into the 
soil (seen here). Clods of dirt usually disintegrate, whereas stones and debris are 
either left in place or occasionally picked up and discarded. On rare occasions wasps 
have been observed to use the same object several times as a compacting tool. S. 
pensylvanicus shows similar packing behavior. 
Fig. 4. S. ichneumoneus disguising the nest entrance. The wasp scrapes the 
region around the nest many times. Leaves, sticks and other debris are grasped with 
the mandibles and either pulled (seen here) over or pushed to the nest entrance or just 
picked up and moved to another location around the nest. The effect of this is that 
the exact location of the entrance is impossible to detect either by the degree of 
compaction of the soil or by the appearance of the area around the nest. Sphex 
pensylvanicus often chews around the nest entrance, breaking down the sides of the 
burrow and leaves a wide depression at the site of the nest entrance. 
