1985] Matthes-Sears & Alcock — Hemipepsis ustulata 257 
and others patrolling the ridge could investigate or land upon the 
landmark during the two trials after which the apparatus was moved 
to a new site. We recorded each “approach” and the total perching 
time at the various artificial landmarks. An “approach” was scored 
when a male tarantula hawk flew directly toward the target on the 
pole and came within 1 m of it. Thus, if a male in a palo verde left 
his perch and flew close to the perch target, then circled back 
around his tree and returned to the target (after having traveled at 
least 2.5 m from the artificial landmark) two approaches were 
recorded. Perching time consisted of the period from first landing 
on the artificial landmark until the male left and did not return or 
until the trial was terminated. 
In order to test the effect of landmark height on male tarantula 
hawks, one experimental perch was set to be about as high (± 0.2 m) 
as the nearby tree, the other extended by the insertion of more 
aluminum tubing to be 1.25 m (± 0.2 m) higher. The order of presen- 
tation of the two types was established randomly. The same perch 
target was used in any given set of experiments; in one series of 14 
paired presentations, the target consisted of four semicircular pieces 
of green cardboard, mottled black and tan, fastened onto thin strips 
of aluminum painted flat black. In another 24 trials, the perch mate- 
rial consisted of green plastic ferns, about 0.5 m long, mounted in an 
aluminum tube that fitted onto the pole (Fig. 1). Ten of the 24 
experiments were conducted in 1981 using four ferns as the target in 
trials that lasted 12 min each; the remaining choice experiments 
were carried out in 1982 using five ferns as the perch target in trials 
that lasted 15 min each. 
In order to test the effect of perch size, two landmarks the same 
height but with different perch targets were placed near occupied 
territories (N = 14 paired trials). Four semicircular pieces of green 
plastic mesh were fastened at right angles to one another with flat 
black aluminum strips and mounted on top of the pole. The larger 
mesh target had pieces 0.5 m X 0.55 m (total area about 0.45 m 2 and 
total volume about 0.4 m 3 ); the smaller target was composed of 
pieces 0.3 m X 0.35 m (total area about 0.2 m 2 , with a volume of about 
0.09 m 3 ). Otherwise the shape and structure of the two targets was 
the same; each was positioned about 1.25 m higher than the nearby 
natural perch. Again the sequence of presentations of the small and 
large targets was random, and each trial lasted 15 min during which 
time approaches and perches were tallied. 
