Menstrual synchrony
Strassmann argued menstrual synchrony defined as menstruation overlap should be quite common. For example, the expected difference by chance between two women with 28-day cycles—which is approximately the average length of menstrual cycles of women at the age —is 7 days. Considering that the mean duration of menses is 5 days and the range is 2 to 7 days, the probability of menstruation overlap by chance should be high.
Trombiculidae
The length of the mite's cycle depends on species and environment but normally lasts two to 12 months. The number of cycles in a year depends on the region. For example, in a temperate region, there might only be three per year, but in tropical regions the cycle might be continuous all year long. Adult harvest mites winter in protected places such as slightly below the soil. Females become active in the spring, and once the ground temperature is regularly above , she lays eggs in vegetation, up to 15 eggs per day. The eggs are round and are dormant for about six days, after which the nonfeeding prelarvae emerge, with only three pairs of legs. After about six days, the prelarva grows into its larval stage.