We compared the population structure of Mesobuthus gibbosus from autumn to mid-summer at two similar phryganic ecosystems, one in continental Greece (Thessalia, near Volos city) and one in insular Greece (eastern Crete). Data were collected monthly using the capture-recapture method. At both sites, density was low during the cold period and increased towards summer. During the samplings, only a small percentage of each population was present. Population density and co-occurrence of scorpions with scorpions or other animals was higher in Crete than in Volos, probably due to the higher inter- and intraspecific competition in Volos. The population structure of the studied species depends on the interspecific competition, the seasonal fluctuations of which influence the intraspecific relations of scorpions, which is reflected in the higher degree of sociality of the insular population.