In Hymenoptera, thanks to its haplodiploid sex determination, arrhenotokous parasitoid females are able to control offspring sex ratio by determining whether to use sperm or not at the time of oviposition. However, the offspring sex ratio may also be influenced by the mating behavior of a male. When a male searches females, he will have more chances to encounter with other males in a high male density population than low male density population. If the male is competitive, the male can find females faster and may have longer copulation time, and eventually transfer more sperm than other males. In this study, we investigated mate searching time, copulation duration and offspring sex ratio as a function of the male density. Although the results show difference between searching time and copulation duration, they are not statistically significant. We will discuss the statistical consequence, male density dependent offspring sex ratio and its evolutionary implications.

This study was conducted in order to investigate and compare anthropometric measurements, bone density, nutrient intake, blood composition and food habits between non-smoking, non-alcohol drinking and smoking, alcohol drinking male university students in Seoul, South Korea. The data for food habits and health-related behaviors were obtained by selfadministered questionnaires. The BQIs of the subjects were measured by Quantitative Ultrasound (QUS). The subjects were divided into two groups: NSND (non-smoking and non-alcohol drinking, n=62) group and General (smoking and alcohol drinking, n=160) group. The results were analyzed using the SPSS program and were as follows: The average heights, weights, and BMIs of the two groups were 173.3 cm, 66.5 kg and 22.1 and 173.4 cm, 68.7 kg and 22.9, respectively. There were no differences between the groups regarding height, weight or BMI. SBP and DBP, however, were significantly higher in the general group than in the NSND group (p〈0.01). The BQIs, Z-scores and T-scores of the two groups were 99.83, -0.23, and -0.31 and 98.24, -0.27 and -0.39, respectively, producing no significant differences between the two groups. The percentages for normal bone status, osteopenia and osteoporosis were 83.88%, 16.12% and 0.0% and 74.37%, 25.62% and 0.01%, respectively. Mean intakes of animal protein (p〈0.05), animal fat (p〈0.05), fiber (p〈0.05), animal Ca(p〈0.05), animal Fe (p〈0.001), Zn(p〈0.05), vitamin B1 (p〈0.05) and niacin (p〈0.05) were significantly different between the two groups, and mean serum levels of SGOT (p〈0.01), SGPT (p〈0.001), γ-GTP (p〈0.001), triglycerides (p〈0.01), total cholesterol (p〈0.05) and hematocrit (p〈0.05) were also significantly different between the two groups. Overall, there were no differences in meal regularity, frequency of snacking, reasons for overeating, exercise and defecation between the groups. However, favorite foods (p〈0.05) and night-time meals (p〈0.05) were significantly different. In conclusion, the health status of the NSND group was superior compared to the general group. Thus, students who smoke and alcohol drink should receive a practical and systematically-organized education regarding the increased health benefits of quitting smoking and alcohol drinking.