26 
Psyche 
[March 
this may have been a relatively common occurrence, since territories 
often changed hands (noticed during periodic scans of the terri¬ 
tories). Non-contact aggressive behavior is known for the males of 
several other species of insects: conocephaline grasshoppers (Morris 
1971), praying mantids (Edmunds 1967), cockroaches (Breed 1972), 
the sphecid Eucerceris flavocinctus (Steiner 1978) and nymphalid 
butterflies (Baker 1972). Baker reported that intruding males in the 
species Inachis io may usurp another male’s territory without 
physical contact, using a behavior similar to the swirling flight. 
One other type of interaction seems to be a form of aggression at 
first glance. A territorial male will drop from a height of approxi¬ 
mately 10 to 30 cm onto the back of a male perched on the ground. 
The perched individual may be within the male’s territory or an 
adjacent territory and does not necessarily have to move to elicit the 
“attack.” The striking male seemingly discontinues the encounter 
himself immediately leaving after a grapple of one second or less. 
Alcock (1975a) refers to this as “strike and flee” in P. multimacu- 
latus. A similar behavior was observed when a male hovered above 
and dropped onto the back of a female working at her nest entrance 
or one that had landed within his territory. As with male-male 
grapples, the striking male orients head-to-head with the female 
when landing upon her. This is the posture necessary to initiate 
copulation. For these interactions the period of grappling was 
longer (several seconds) and was terminated when the female 
managed to break free of the male’s grasp. Occasionally two males 
were seen simultaneously grappling a female in this manner. Upon 
breaking free,' the female continued working on the nest or flew 
away a short distance, perching on the sand for a short period of 
time before returning. The latter behavior is similar to parasite 
avoidance noted for this and other species of Philanthus (Evans 
1970) and may function to reduce the number of energetically 
expensive encounters with males. The encounter may be repeated 
and may result in the female losing her prey. The similarity of this 
behavior (“strike and flee”) towards both males and females sug¬ 
gests that the motivation behind it is the same. In other words, the 
male is pouncing upon a potential mate and terminates the inter¬ 
action himself when some proximate cue signals that it is not a 
conspecific female. This has been suggested as an explanation for a 
similar form of male-male interaction in the western cicada-killer 
wasp, Sphecius grandis (Alcock 1975b). Therefore, the swirling 
