36 
Psyche 
[March 
This may be the situation in P. psyche and other species in the genus 
which scent mark. Even in a short-range communication system, 
conservation of energetically costly pheromone supplies should 
involve consideration of wind speed. 
There is a line of morphological evidence supporting the idea that 
abdomen dragging serves to scent mark. Two parts of the males 
body (excluding the legs) are in contact with the plant while 
abdomen dragging occurs, the mandibular area and the distal venter 
of the abdomen. A small tuft of hair, termed the clypeal brush 
(Bohart and Grissell 1975), is located near the base of the mandibles 
at the point where the head touches the plant. It is possible that the 
pheromone could be applied to the plant via the clypeal brush, the 
chemical itself being produced in the mandibular glands (Gwynne 
1978). Close examination of the brush (prior to preservation in 
Bouin’s solution) reveals that the hairs adhere to one another as if 
saturated with a liquid. Hair tufts are known to be associated with 
the deposition of trail pheromones in ants (Fletcher and Brand 
1968). 
Dissection of the male heads reveals a large pair of mandibular 
glands which nearly fill the portion of the head cavity beneath the 
eyes. This is also true for P. bicinctus (Gwynne 1978) and other 
species of Philanthus which I have examined ( gibbosus, tarsatus, 
zebratus, crabroniformis and pacificus). The last two also have 
clypeal brushes but are not known to set up territories or to exhibit 
abdomen dragging, so it is possible that the glands serve some other 
function. P. albopilosus is the only species that I have examined in 
which the males have neither clypeal brushes nor large mandibular 
glands. This species does not exhibit abdomen dragging or establish 
territories (Evans 1975). The presence of clypeal brushes in most 
Philanthus, as well as in other genera of the subfamily Philanthinae, 
suggests that the absence of the brush in this species is a derived 
character. The mandibular gland as a source of pheromones is well 
documented in the Hymenoptera (Wilson 1971). 
The third structure associated with the deposition of a pheromone 
is a brush of hair on the venter of the abdomen which is more diffuse 
than the clypeal brush but covers a wider area. There are no known 
glands associated with the hair brush (Evans personal communica¬ 
tion). This hair brush may serve to spread the pheromone more 
evenly on the stem, facilitating evaporation. The abdominal and 
clypeal hair brushes are not present in females of this species. While 
