1979] Matthews, Hook & Krispyn — Behavior of Crabro 157 
o 
Figures 6-7. Profiles of typical Crabro argusinus spring nests from (6) the boiler 
site, and (7) the north beach site. Cells are numbered according to apparent order of 
provisioning based upon larval development. Black dot indicates point where prey 
flies were stored in burrow prior to transfer to a cell. Scale bar is 5 cm. 
Hunting behavior and prey capture was observed on several occa¬ 
sions at the north beach site. Females flew slowly into the wind 
along the high tide line where salt marsh reeds and other debris had 
accumulated along the base of the cliffs. Prey appeared to be 
detected visually as they rested on the white sand as wasps were 
frequently seen to dart at small dark pebbles of the same size as the 
flies. Upon spying a potential prey item the wasp hovered momen¬ 
tarily about 10 cm downwind of it and 6-8 cm above the substrate, 
then suddenly it darted forward very quickly and pounced upon the 
prey in an attack aptly described as “hit and run”. It was possible to 
walk alongside of individual females for several meters as they flew 
slowly along pouncing on one object after another until they were 
finally successful in capturing a prey item. In contrast to the major¬ 
ity of other species of Crabro, C. argusinus prey were clearly para¬ 
lyzed and not necessarily killed. 
In addition to the physical differences between these two study 
localities, differences in the abundance of parasites were also strik¬ 
ing. At the more localized and protected boiler site miltogrammine 
flies were excessively common and reflecting this, the incidence of 
