The effects of body size on mating success and duration of copulation were investigated in Pyrrhocoris apterus. Under laboratory conditions relative mating success of small and large males was investigated in groups of 2 males (majority sex) : 1 female (minority sex). Large males were recorded significantly more often in copulation than small males when the female was large but not when the female was small. This was also the case when the group size was 24 males : 12 females or population density decreased by increasing the area of the experimental arena. In groups of 2females : 1 male, large females were recorded in copulation significantly more often than small females when the male was large but not when the male was small. Proportion of individuals of the minority sex that copulated was similar for males and females, regardless of body size. The average duration of copulation was similar for small and large males, but shorter for small than large females. The difference in the duration of copulation of small and large females was greater when it was with small rather than large males. The prolonged guarding of large females by small males may be explained by a trade-off between increasing the probability of inseminating an uneasily accessible high quality partner and copulating with more females.
A series of experiments were conducted to compare the susceptibility of P. regina larvae reared in isolation or in groups to the effects of diet-borne metabolic inhibitors: chlorogenic acid (CGA) and mimosine. Larvae were presented with diets containing 0.4 mM CGA or 0.4 mM CGA in combination with 22 mM lysine or methionine or with diets containing 1.5, 15 or 30 mM concentrations of mimosine. Methionine and CGA caused significantly reduced pupal weights when compared with larvae presented with lysine and CGA. All concentrations of mimosine resulted in 100% mortality with larvae unable to successfully complete pupation even at the lowest concentration. In general, larvae reared in groups were less susceptible to the toxic effects resulting from diet-borne metabolic inhibitors. The results are discussed in relation to the chemical factors that result from the feeding activity of saprophagous dipterans.
Golden takin (Budorcas taxicolor bedfordi; Bovidae), is found only in the Qinling Mountains of western China. Radio-tracking and direct observations were carried out at Foping Nature Reserve in Shaanxi Province to study social behavior of the takin, including group sizes, group composition and group stability. Golden takins are gregarious. Mean group size among 1,039 takins sighted in groups was 10.82 ± 0.96 (n = 96) individuals excluding solitary individuals. The largest group had 59 animals and 50% of the animals were seen in groups larger than 15 individuals during the study period. The results from this study indicate that the core social unit of golden takin is adult females accompanied by their offspring of more than one generation. 53.1% of all groups included more than one adult female, and 63.3% of all groups had more than one subadult or calf. The mean size of groups formed by adults with subadults or calves was 14.83 ± 2.34 (n = 29) individuals. The ratio of adult females to adult males was 1.0 : 0.49, skewed in favor of females. The results also show that takin groups are unstable and group composition can vary over time. Reproductive activity of adult males, subadult leavings from their mother’s group and human disturbance are suggested to be factors responsible for group size variation.