Abstract
Nests of Lindenius pygmaeus armatus were examined in northern Poland in Kowalewo Pomorskie and Sierakowo. Adults were encountered from late May to late July. The nests were built in sandy areas and wasteland. Seven nests were observed, of which two were dug up and their structure was examined. The channel was approximately 2.5 mm in diameter and 8-10 cm in the length. The material removed during digging was placed near the nest entrance. The main burrow led to 3-5 cells. The cocoons were approximately 5-7 mm long and 2.5-3.5 mm wide. Females of L. p. armatus provided their nest cells with chalcid wasps averaging 14 prey items per cell. Parasitoids Myrmosa atra and kleptoparasites Senotainia conica were observed entering the burrows. Both females and males of L. p. armatus were detected on the flowers of Achillea millefolium, Peucedanum oreoselinum, Daucus carota, and Tanacetum vulgare. The article also includes phylogenetic relationships of Western Palearctic Lindenius species.