The regulation of activity in populations of the terrestrial slug Limax maximus (Gastropoda; Limacidae)

Summary The activity of the slug Limax maximus was studied in relation to weather. Three hundred‐and‐fifty‐eight hourly observations of activity and weather were made on 21 nights from May until October, 1976. Factors causally important to molluscan activity were included in a step‐down correlation‐regression analysis of daily and seasonal behavior. The analysis was also performed using weather data from the previous hourly observation. Models using lag‐weather did not explain as much variability as did concurrent weather. The regression models explained about 73% to 87% of the observed variation in activity. The most important factors included in the regression models were time of day (circadian rhythm), light intensity, changes in light intensity and surface temperature. Shelter temperature, temperature gradients, length of the night, and time of sunset were also included in some models. Age and hydration were shown to be key factors in other experiments. A model incorporating weather thresholds estimated from field data explained 83.06% of the variability in the activity of L. maximus over the season. The values predicted from the model did not differ significantly from those actually observed in the field (Kolmogorov‐Smirnov test, p>0.50).