harsh conditions of the winter. The sex ratio of the offspring also depends on the distance between nesting and foraging sites. Females have been observed and determined to bias their offspring sex ratio to males at larger flight distances from the nest. Kin recognition and fratricide Research on second-generation bees illustrates that kin recognition of nest mates is not a genetically based behavior. Further, fratricide has been hypothesized to be a nondiscriminatory behavior; emerging individuals treat developing siblings and nonsiblings similarly. When developing in cells behind diapausing bees, inner-nesting bees either bypass the nest in front of them, retreat back to their nests until diapausing individuals emerge, or chew through the nesting cells in front of them, killing the diapausing bees. These decisions are contingent on the extent of development of delay of nestmates. For example, emerging individuals would remain in their cells when they were delayed from emerging for a relatively short period of time. When delayed for longer periods of times, however, emerging individuals would use their mandibles to destroy the cells of their nest mates. With respect to gender differences, males have been observed to bypass nests more frequently than females due to the small size of males. Sexual behavior Mating M. rotundata has been found to be a monandrous bee species. During the mating season, males attempt to obtain mates by positioning themselves at sites where female are likely to be, including foraging sites and nests. While females can mate several times, they resist male advances by restricting their mating to one sexual interaction and fleeing from these males. This behavior is attributed to female productivity during the construction of her nest and egg-laying. When harassed, females are unable to build their nests efficiently, making less foraging trips and spending a longer time overall in nest construction. Fleeing allows females to avoid being mounted. In the process of fleeing, however, females may lose their nesting materials, such as leaves and must then make an additional trip to make up for the lost materials. Sexual pheromones Sexual pheromones in epicuticular waxes are released by females to assist in attracting males as mates. Studies of the emissions from these waxes reveal that alkenes are the primary compound detected by males. Further, females of different ages emit different pheromones, containing different alkene compositions. In young females, substances that classify as either 7-pentacosene or 9-pentacosene are present in the highest