1985] 
Matthes-Sears & Alcock — Hemipepsis ustulata 
259 
After each pair of presentations, the artificial landmarks were 
moved to a different tree so that no one resident male was given 
more than one opportunity to respond to a particular pair of 
landmarks. 
Means are expressed ± 1 S.D. 
Results 
The Effect of Height on Landmark Perch Attractiveness 
When given a choice between approaching or perching on two 
targets, one of which was elevated 1.25 m above the other, male 
wasps clearly preferred the higher target (Table 1). When the perch- 
ing material was cardboard, the wasps approached the taller land- 
mark significantly more often (W = 284.5, p < 0.0001; Wilcoxon 
two-sample test). The same result applied to the two experiments in 
which plastic ferns were employed as a perch target (1981: W = 
147.5, p = 0.0022; 1982: W = 282.5, p = 0.0005). Although for some 
reason males refused to take up residence upon the cardboard 
perch, they regularly did so when the target consisted of artificial 
ferns, but only on the taller of the two available landmarks (X 2 = 
26.32, p< 0.0001, for the combined 1981 and 1982 results). Of the 
17 individuals that claimed artificial landmark perches, 12 were 
residents in a nearby tree that abandoned their territories to move to 
the higher but completely unnatural perch sites. The other five 
Table I. The effect of height of artificial perches on the frequency with which 
male tarantula hawks approached and perched on them during 15-min trials. 
Number 
Number 
Perch 
Perch 
of Paired 
Mean 
Mean 
of Males 
Material 
Height 
Trials 
Approaches 
Perching Time (min) 
Perching 
Cardboard 
High 
14 
15.1 ± 11.2 
0 
0 
Low 
3.1 ± 4.0 
0 
0 
Plastic 
High 
10 
17.9 ± 11.1 
5.3 ± 5.6 
7 
Ferns 
( 1 98 1 ) a 
Low 
4.5 ± 4.9 
0 
0 
Plastic 
High 
14 
22.2 ± 13.5 
5.4 ±5.2 
10 
Ferns 
(1982) 
Low 
4.9 ± 5.7 
0 
0 
a 1 98 1 trials lasted 12 min each. 
