1979] Matthews, Hook & Krispyn — Behavior of Crabro 165 
north beach site where nests were also typically widely spaced. Since 
time did not permit following the above 4 nests to completion, all 
were excavated late in the day that they were initiated. In every case 
the burrow excavation was still incomplete and no prey had yet been 
stored. This indicates that C. argusinus requires at least one day to 
excavate the main tunnel. 
Discussion 
Like all known Crabro, C. hilaris and C. argusinus nest in sandy 
soil and prey upon a variety of Diptera. C. hilaris prefers stockier- 
bodied flies, primarily muscoids whereas argusinus utilizes a wide 
diversity of prey, but prefers ephydrids and dolichopodids. C. hilaris 
inhabits inland protected locations in flat soil, whereas C. argusinus 
characteristically nests in close association with water and prefers to 
nest in slopes or in the sides and “corners” of depressions in rela¬ 
tively flat open sand. 
Striking differences in the behavior and nest parameters of the 
two populations of C. argusinus studied at the same season may be 
due to differences in both biotic factors (available prey and parasite 
pressure) and physical factors (erosion, wind, etc.). The larger 
number of prey stocked per cell at the north beach site may in part 
reflect the absence of parasites and in part a preference for smaller 
sized prey. It may also reflect different hunting habitats, beach ver¬ 
sus salt marsh; larger flies may be more accessible in the marsh. At 
the boiler site, the presence of strong parasite pressure may have 
caused wasps to finish provisioning sooner. The greater depth of 
cells at north beach possibly reflects the relative instability of that 
habitat where erosion continually whittled away at the cliff bank. In 
contrast, the boiler site has probably changed very little in the many 
years since the boiler was abandoned. However, reasons for the 
much greater depth of spring nests as compared to that of fall nests 
at north beach are unknown. The road site where the shallowest 
nests were found was very compacted sand with innumerable roots 
which caused nests at this site to be very contorted. It may be that 
digging behavior is genetically controlled and shut off after a prede¬ 
termined amount of energy is expended which would vary between 
localities and seasons. 
In overall biology these two species fit the typical Crabro pattern 
on all traits enumerated by Kurczewski and Acciavatti (1968) and 
summarized by Bohart and Menke (1976). Nevertheless, variation 
