In 2000 2002 droppings were collected in ca. 2 weeks intervals under the emerging hole of nursery colony of Pipistrellus pygmaeus (Leach, 1825) dwelling (occupying) spaces under the roof of a game keepers log-cabin situated inside floodplain forest extended between lower parts of the Dyje and Morawa rivers up to their confluence (Southern Moravia, Czech Republic). In total, 27 samples of droppings (each consisted of 20 pellets) were used to analyze of food remains. In the diet 40 taxonomic groups of invertebrates were found (Tab.). As expected, small dipteran insects were the main food items from which Nematocera dominated (60 per cent of all items). Besides families Chironomidae and Ceratopogonidae high percentage of nematoceran eggs was also recorded. Relatively high frequency of Brachycera was surprising (7,2 %). Further often food items consist of orders, i. e. Trichoptera (9,4 %), Hymenoptera, Coleoptera and Sternorrhyncha (each ca. 3,5 %). There were no between-year differences (2000-2002) in the percentage of particular prey group (ANOVA, F = 5.78, p = 0.158, df = 48). The study period was divided into four parts with respect to bat reproduction, i. e. pregnancy (until June 15th), lactation (from June 16th till July 13th), post-lactation (from July 14th till August 11th) and movement period (after August 11th). The significant fluctuation was found only in Nematocera (F-test, F = 2.54, p = 0.048, n = 27), Nematocera eggs (F = 9.81, p = 0.001, n = 27), Muscoidea (F = 2.60, p = 0.046, n = 27), Tipulidae (F = 6.75, p = 0.001, n = 27) and Heteroptera (F = 6.47, p = 0.001, n = 27) during the season. The research was supported by the grant of the Czech Science Foundation No. 206/02/0961 and the grant of the Ministry of Education, Young and Sports of the Czech Republic No. MSM0021622416.