1. The influence of sun exposure and moisture on reproduction and size of a north temperate dung beetle Aphodius fossor was investigated. Adult beetles were added to cow pats that were either shaded or exposed and treated with different watering regimes.
2. After 26 days, more eggs and larvae were recovered from shaded and wetter pats than from exposed and drier pats.
3. At the end of the experiment, more beetles had developed in shaded and wetter pats, and these beetles were larger than those from exposed and drier pats.
4. There was no between-treatment difference in the ratio between adults in final sampling and larvae in first sampling.
5. It was concluded that exposure and moisture can influence both reproduction and size of A. fossor. It is suggested that weather may be a factor regulating reproduction in Aphodius not only through heat- or drought-induced mortality, as suggested earlier, but also by limiting the time available for egg laying. Further studies are needed to clarify this suggestion.