Bursaphelenchus debrae n. sp. was cultured from dauer juveniles recovered from the poison sac of a female sweat bee, Halictus brunnescens from Ankara, Turkey, in June 2004. The new species appears to be most similar to B. kevini and B. anatolius based upon the synapomorphies of their associations with soil-dwelling halictid bees, morphological features such as four lateral incisures, male caudal papillae arrangement, spicule morphology, female tail shape and ratio a, and molecular analysis of sequences of the D2/D3 expansion segments of the large subunit (LSU) rDNA and partial mitochondrial DNA COI (mtCOI). In addition to significant molecular sequence differences in LSU and COI consistent with separate species status, B. debrae n. sp. can be differentiated from both B. kevini and B. anatolius by differences in the host halictid bee species with which they are phoretically associated, rostrum shape and size, and presence of a unique protuberance on the ventral aspect of the spicules. The nematode is mycophagous and can be cultured in the laboratory at 23 degrees C on Monilinia fructicola growing on lactic acid-treated, 5% glycerin-supplemented potato dextrose agar (LGPDA).