Variations in female percentage in progenies of Armadillidium vulgare females carrying the f element at different population levels. (a) Variation among six natural populations (data from [59,62]); n is the number of progenies, while i is the total number of individuals. The locations of the populations were the United Kingdom (Northampton), the Canary Islands in Spain (Marazul), and France (Moulis, Camarade, Ile d’Yeu and Niort). The average female percentage across the six populations is 62%. (b) Variation within a single population. Distribution of 28 progenies from females sampled in Niort, France (data from [62]), according to female percentage.