32 
Psyche 
[March 
Abdomen Dragging and Scent Marking 
A common behavior of males on territories is abdomen dragging. 
All species of Philanthus known to be territorial exhibit this 
behavior. Abdomen dragging begins by the male flying from his 
perch on the sand to a plant in or bordering his territory (usually 
blowout grass or lanceleaf scurfpea). Upon landing, the male walks 
along the stem or leaf in an inverted V position, the mandibular area 
and the posterior venter of the abdomen touching the plant. The 
abdomen is also “waggled” back and forth while in contact with the 
stem The average number of times a male dragged his abdomen in a 
5 minute period was 7.75 (N = 20; S.D. = 3.8). Alcock (1975a) has 
suggested that a pheromone is being deposited by the male during 
abdomen dragging functioning to attract conspecific females to the 
territory for the purpose of mating. Although no bioassays were 
conducted, several lines of evidence suggest that this may be the 
case. 
In nearly all cases (e.g., twenty-three of twenty-five for one male) 
abdomen dragging is preceded by what I will term a weaving flight. 
The male leaves his perch and flies back and forth about 10 cm 
above the ground, always perpendicular to wind direction and 
facing into it. The lateral portion of the flight is wide (up to about 30 
cm) at first, but usually narrows down to the vicinity of one upwind 
plant (Figure 4). I have also observed a similar flight in P. pulcher 
and P. tarsatus (unpublished). P. multimaculatus also makes short 
flights downwind of and facing the plant on which it perches and 
drags its abdomen (Alcock 1975a). If a chemical is being deposited, 
economical use of the male’s pheromone supply could involve some 
way in which he could receive feedback on the airborne concentra¬ 
tion in order to regulate the rate of scent marking. The weaving 
flight places the male in a position to detect the pheromone since he 
is downwind of the source. Interestingly enough, although a weav¬ 
ing flight usually precedes abdomen dragging, it often ends with the 
immediate return of the male to his perch. At some point during the 
weaving flight the male (after testing the airborne pheromone 
concentration) may make the decision whether to scent mark or not 
Wind direction affects the behavior of males associated wit 
abdomen dragging and the weaving flight. For five males observed 
only seven of two hundred and'six (3.4%) abdomen draggings were 
on plants downwind of the'perch, while one hundred eighty-two 
(88.3%) and seventeen (8.3%) were on plants upwind of and lateral 
