DIFFERENCES IN THE LIFE HISTORIES OF XEROLENTA OBVIA (MENKE, 1828) (HYGROMIIDAE) IN A COASTAL AND A MOUNTAINOUS AREA OF NORTHERN GREECE

The life cycle of Xerolenta obvia (Menke, 1828) was studied in two areas, Paleokastro (Chalkidiki), an inland mountainous area, and Nea Karvali (Kavala), a coastal area in northern Greece. At Paleokastro snails hatch in autumn, become adult the following July, but do not lay eggs until October, after which they die. Clutch sizes are small, but eggs and hatchlings are large compared with those at Nea Karvali. Growth is fast in spring, and continues until the end of July. The young hatchlings have dark shell-bands, but by July a quarter of snails appear unbanded. At Nea Karvali, eggs are also laid in October, and young snails emerge from hibernation in March. Here, however, they do not mature until April of the following year. They thus have a 2-year life cycle, with adults dying in their second autumn. Clutches are about three times the size of those at Paleokastro, but eggs and hatchlings are significantly smaller. A little growth occurs in winter, but the rate of growth is generally much slower than at Paleokastro. Only 1–2% of this population has banded shells; the bands are less obvious and they become invisible in some individuals as they mature. At both sites population density fluctuated during the two study years, but it was always higher at Nea Karvali. These results are discussed in relation to the differing climates of the sites, and comparisons made with studies on related species in the region.