454 
Psyche 
[Vol. 92 
analysis between P. aurifacies activity and cell depth yielded an r 2 
value of 0.42 (ANOVA F = 10.28, p < 0.01). 
Senotainia vigilans 
S. vigilans was present throughout the nesting season of A. harti 
(Fig. 1). During the first generation of A. harti, S. vigilans was more 
active in the morning than in the afternoon (Fig. 2). This coincided 
with the period of greatest activity of first generation females of A. 
harti and other wasps present in the sand pit. In the second genera- 
tion of A. harti, S. vigilans was equally active in both the morning 
and afternoon (Fig. 2). 
S. vigilans was attracted to movement and, therefore, trailed 
wasps constructing, inspecting, or provisioning nests. Flies either 
hovered 2-15 cm above and behind a female while darting close to 
the wasp or her prey, or perched on a nearby elevated site (e.g., 
pebble, plant) and watched the wasp from there. In attempting to 
larviposit on the prey, 5. vigilans exhibited two, not mutually exclu- 
sive, behaviors: (1) landing on the prey at the nest entrance or as it 
was being taken inside; and (2) entering the nest (following the 
provisioning wasp into a nest), (see Spofford, et al., 1986.) 
Of 105 observations of S. vigilans attracted to A. harti provision- 
ing their nests, flies landed on the prey 25.7% (27 of 105) of the time. 
Some S. vigilans landed and larviposited on prey during transport 
to the nest, but most landed on the prey either while the wasp was 
opening the nest or as she took the prey inside. 
Flies entered the wasps’ burrows 47 (44.8%) times. It was uncer- 
tain whether or not entering flies larviposited on the prey or in the 
burrow, or left without larvipositing. Some flies did not travel far 
into the burrow and most reappeared less than 2 sec after entry. 
Two flies reappeared in entrances shortly after the wasps, indicating 
that they had “crossed paths’’ in the burrow. Flies attracted to 
provisioning A. harti did not attempt to larviposit 29.5% (3 1 of 105) 
of the time. These flies either continued to hover, were distracted by 
another wasp in the vicinity, or were eluded by the wasp (see 
counter-cleptoparasitic behavior). 
The success frequency of the “landing” strategy was high (Table 
1). Larviposition occurred 20 of 27 (74.1%) times when the fly 
landed on the prey. It could not be ascertained if larviposition actu- 
ally occurred when a fly entered the nest because the fly was not 
visible. Therefore the presumed parasitism numbers (« success fre- 
