1985] 
Hager & Kurczewski — Cleptoparasitism 
457 
or presence of cleptoparasitic flies. In the absence of flies, the mean 
number of trips into the burrow for sand removal was 4.7 ± 4.51 
(range 1-26, N = 94). With flies present, either hovering behind or 
perching nearby, the intensity of the cleaning behavior increased 
significantly to 9.5 ± 4.97 trips (range 1-17, N = 23; t = 52.28, 1 15 
df, p < 0.05). 
Discussion 
The main advantage of progressive provisioning is generally con- 
sidered to be the greater protection from enemies afforded the egg 
or larva due to the prolonged presence of the female (Evans, 1966). 
The female may remove or destroy cleptoparasites or provide more 
food to a parasitized nest and thus prevent starvation of the larva. 
Since most provisioning trips to a nest occur after the egg has 
hatched, the cleptoparasite will usually be introduced to a larva. In 
this case, the larva may be able to outcompete the maggot (clepto- 
parasite) and thus indirectly kill it, or it may directly destroy the 
maggot by feeding upon it. 
With this in mind, we can now consider several predictions for the 
effects of cleptoparasitism on A. harti: (1) cleptoparasites will 
almost always be successful if they attack the initial prey in a cell 
(while the wasp is still in the egg stage); (2) successful cleptoparasit- 
ism should decrease as the larva matures; and, (3) the larva may be 
the essential component in cleptoparasitic defense by consuming or 
outcompeting the maggot (cleptoparasite). 
P. aurifacies, a closed nest searcher, had little or no effect on the 
reproductive success of A. harti. Cells were found to be deeper in the 
first generation when P. aurifacies was present, but the significance 
of this correlation remains questionable. Other factors (e.g., soil 
moisture) may influence cell depth. Reasons for why hole-searching 
cleptoparasites are not successful in parasitizing A. harti include: (1) 
the stone used to close the nest entrance provides a physical barrier 
to a burrowing maggot deposited in the entrance; (2) removal of the 
tumulus from the vicinity of the entrance may aid in its concealment 
and therefore P. aurifacies may be unable to detect (locate) the 
entrance; and, (3) A. harti cleans the burrow and, in so doing, may 
remove any maggots placed therein. 
Senotainia vigilans, on the other hand, had limited success in 
cleptoparasitizing A. harti nests. This success depended upon the 
