1985] 
Hager & Kurczewski — Cleptoparasitism 
461 
sand that might otherwise block the burrow. The presence of the 
adult fly may serve as a cue that stimulates further burrow cleaning. 
This then enables the wasp to bring the prey in more quickly during 
the next provisioning and decreases the exposure time of the prey to 
cleptoparasites. 
Nesting in aggregations may reduce cleptoparasitism through the 
selfish herd effect (Wcislo, 1984). A. harti may nest in one location 
not only because it contains all of the physical requirements but also 
because those individuals nesting in a congested area may limit the 
amount of cleptoparasitism of their nests. Wcislo (1984) suggests 
that this works best against hole-searching cleptoparasites but we 
feel it can be extended to include satellite flies. S. vigilans was often 
distracted from following a provisioning wasp by the movements of 
another wasp nearby. A wasp adopting the strategy of remaining 
still after having been spotted by a satellite fly may have an 
increased chance of evading the fly when it is within a nesting 
aggregation. 
Acknowledgments 
We thank N. E. Woodley and W. L. Downes, Jr. for identifying 
the flies, A. S. Menke for confirming the wasp species, and M. G. 
Spofford for assistance in the field. We also thank W. M. Shields for 
reviewing the manuscript and offering useful comments. This work 
was partly funded in 1982 and 1983 by Grants-in-Aid of Research 
from Sigma Xi, the Scientific Research Society. 
Literature Cited 
Alcock, J. 1975. The nesting behavior of Philanthus multimaculatus Cameron 
(Hymenoptera: Sphecidae). Am. Midi. Nat. 93: 222-226. 
Allen, H. W. 1926. American species of two-winged flies belonging to the tribe 
Miltogrammini. Proc. U.S. Nat. Mus. 68: 1-106. 
Alm, S. R. and F. E. Kurczewski. 1984. Ethology of Anoplius tenebrosus 
(Cresson) (Hymenoptera: Pompilidae). Proc. Entomol. Soc. Wash. 86: 110-119. 
Evans, H. E. 1963. The evolution of prey-carrying mechanisms in wasps. Evolu- 
tion 16 : 468-483. 
Evans, H. E. 1966. The comparative ethology and evolution of the sand wasps. 
Harvard Univ. Press, Cambridge, Mass., 526 pp. 
Evans, H. E. 1970. Ecological-behavioral studies of the wasps of Jackson Hole, 
Wyoming. Bull. Mus. Comp. Zool. 140 : 451-51 1. 
