Mating success and nutrient reserve effects on queen survival and nest initiation were examined with respect to the reproductive fitness of queens of the baldfaced hornet, Dolichovespula maculata. The sperm content of the Spermatheca was examined in queens of this hornet species and in queens of 10 other yellowjacket species collected in spring and summer of 1987, 1988 and 1989. Queens of the baldfaced hornet, D. maculata, were also analyzed for sperm content prior to nest initiation and during colony development. A regression model was employed to determine sperm utilization. Based on total cell counts and adult census, the sperm use efficiency of this species changed from approximately 90-100 sperm released per egg in the initial stages of colony development, to 2-3 sperm released per egg after 1000 eggs had been laid. Near the end of the season the predicted number of sperm released per egg was 0-1. The number of sperm in D. maculata males ranged from 2-2.5 million; a value considerably greater than the mean sperm number (20,223; ±4,669) found in mated spring queens (n=15). Nineteen (18.4%) of 103 yellowjacket queens analyzed in the spring seasons of 1987 and 1988 were uninseminated. The effects of mating success and sperm utilization on colony development are discussed. A significant regression of sperm content on colony size was also found for 8 species of yellowjacket. Queens of D. maculata were collected for studies of nutrient reserves before hibernation in the fall, during nest initiation, and after colonies had produced more than 2 worker broods. Fresh and dry weights were determined for all queens and a seasonal comparison of the energy reserves of lipids, sugar, and glycogen was performed on the thoracic and abdominal tagmata. Total nitrogen was also quantified to estimate protein changes by season. The results show that lipids accounted for 35% of the weight lost during hibernation, sugars 12%, and glycogen 6%. Total thoracic nitrogen remained constant throughout the year, whereas abdominal nitrogen was the same in the fall and spring queens but increased in the summer queens. The results from this study suggest that most queens which survive the winter and successfully initiate nests have similar energy reserve quantities. The implications of these findings to solitary foraging behavior are discussed. The eggs of D. maculata were examined in the spring and summer to quantify the energetic contributions provided by the queen. Mean egg weight was highest in the spring and decreased with progressive nest development. Both egg weight and energy reserves were variable among and within nests. The nutrient reserves for eggs in embryo nests, in order of importance, were lipid (22%), glucose (9.5%), and glycogen (5%). A 10-day egg incubation experiment demonstrated a mean loss of 83 ug dry weight; lipids could not completely account for the weight loss, either quantitatively or qualitatively. A study on egg developmental time failed to provide sufficient data; all eggs eventually died although embryonic larval movement was detected in 2 eggs after 16 days. The energetic contributions which a queen provides to the eggs are discussed with respect to foraging behavior and environmental influences. / Ph. D.