34 
Psyche 
[Vol. 87 
would be further enhanced if males focused their territorial activity 
around active nests. If females exercise a preference for presence of a 
guarding male prior to initiating nesting (e.g. Trypargilum), then this 
behavior would spread in the population, since it would directly 
benefit the interests of both sexes. The possibility exists that males 
could ultimately be induced to guard nests without requiring 
repeated matings as is reported for Tachytes distinctus (Lin, 1963; 
Lin and Michener, 1972). However, such cases are in need of further 
study. In digger wasps, delays in provisioning and exposure to 
predators and cleptoparasites constitute important risks for females; 
but rejection of males may be costly in terms of time, energy and loss 
of resource (the nest). Such costs to the female must be important, 
otherwise females of O. sericeus would not often attempt to sneak 
past guarding males when provisioning. Guarding males also incur 
real costs in addition to time and energy expenses. Gwynne and 
O’Neill (1980) recently showed that territoriality in Philanthus males 
resulted in increased mortality due to sex-biased predation. In 
Oxybelus sericeus the balance struck appears to effect a significant 
reduction in levels of cleptoparasitism, so male guarding directly 
benefits the interests of both sexes. 
Summary 
The multivoltine wasp Oxybelus sericeus nested continually from 
early May to October on St. Catherine’s Island, Georgia. Nest sites 
were situated in sand just above a tidal salt marsh where the females 
hunted prey. Two otitid flies, Chaetopsis apicalis and C. aenea and 
one dolichopodid, Nanomyina litorea, comprised 96% of the prey. 
Up to three cells per day were stocked with an average of 7 (range 3 to 
14) flies per cell. Prey were transported pedally from point of capture 
to the nest area whereupon females either continued pedal transport 
or impaled the fly on the sting before continuing to the nest. Number 
of cells per nest averaged 1.7 (range 1 to 6) with individual females 
varying the number of cells in successive nests. Cell depths averaged 
7.9 cm (range 3.5 to 15). Males were active in the nest area and utilized 
five different mating strategies. Patrolling and nest guarding were the 
most common strategies. Certain individuals were found to dominate 
all other males in encounters in a small nesting area. These dominant 
males shifted their guarding activities to “track” actively nesting 
females for up to seven days. Miltogrammine fly parasitism ranged 
