Neotypus pusillus in Europe is a parasite of the obligatory myrmecophilous lycaenid butterfly Maculinea nausithous. It was recorded for the last time in Poland at the beginning of the 20th century on a few sites in Lower Silesia and on one site near Poznan. During the present studies we found Neotypus pusillus in two other regions: in Polesie (eastern Poland) and in Upper Silesia. On both sites adult females were observed ovipositing on flowerheads of Sanguisorba officinalis L. with M. nausithous caterpillars inside. Additionally we reared two males from parasitized pupae. N. pusillus is probably more widespread in Poland but restricted to big populations of M. nausithous. Some remarks about the biology and ecology of the parasitoid are included in the paper. Maculinea nausithous (Lycaenidae) : Host Neotypus pusillus (Ichneumonidae) : Parasite New record Parasites diseases and disorders; Parasites; Insect parasites; Hosts; Insect hosts; Land zones; Palaearctic region; Eurasia; Europe Maculinea nausithous; Hymenopteran parasites; New host records; summary of country-wide distribution & biology; Neotypus pusillus; Poland; Polesie & Upper Silesia Neotypus pusillus; Lepidopteran hosts; New host records; summary of country-wide distribution & biology; Maculinea nausithous; Poland; Polesie & Upper Silesia none