Due to importance and effectiveness of some entomopathogenic or insect parasitic nematodes in controlling of agricultural pests, or pests of non-agricultural plants, a study was conducted in order to identify the species of this group of nematodes in city of Tehran. As the result, three species belonging to the genus Oscheius were recovered in association with bark samples having the bark beetle galleries. Morphological and molecular data were provided for two recently recovered species of the genus, namely O. necromenus and O. onirici. Molecular data were also provided for a recently recovered isolate of O. tipulae. All three species were recovered in association with bark samples collected from dead trees in the city of Tehran. Morphological characters and morphometric data of the two aforementioned species are in accordance with the data given in their original descriptions. One recovered individual from a small bark sample characterized by its short body length was sequenced for its 28S and internal transcribed spacer (ITS) rDNA loci, and the results of BLAST search using the newly obtained partial sequences revealed that it belonged to O. tipulae. Molecular phylogenetic studies revealed recently sequenced Iranian populations of O. onirici and O. tipulae forming a clade with other isolates/populations of these species in ITS tree with maximal Bayesian posterior probability (BPP), and presently sequenced isolates of O. tipulae and O. necromenus form a clade with other isolates of these species in 28S tree. The two species O. onirici and O. necromenus were reported in Iran for the first time.

Parasitorhabditis obtusa is reported from Iran for the first time. The studied population is characterised with its morphological and molecular data. Morphological characters of the recovered population is in agreement with the currently available data of the species. In molecular phylogenetic studies using partial sequences of 28S rDNA D2/D3 fragment, the species formed a clade with two other isolates of the species with maximal Bayesian posterior probability (1.00) and maximum likelihood bootstrap values (100). The species was in association with bark samples of dead coniferous trees having galleries of bark beetles. It was also recovered from inside of the body of the Mediterranean pine beetle, Orthotomicus erosus, representing a new insect host for this nematode species.

Summary A new species of Scutylenchus was recovered from soil collected in the rhizosphere of forest trees in natural Asalem forests, Gilan province, north Iran. The new species is described and illustrated based upon morphological and molecular data. Scutylenchus quercinus n. sp. is mainly characterised by having four lines in the lateral fields, thus delimiting it from currently known species of the genus, which have six lines. It is further characterised by 605-709 μm long females having a slightly offset cephalic region with five or six annuli, stylet 19-21 μm long with conus ca 50% of its total length and three slightly posteriorly sloping knobs, vulva in a cavity, with epiptygma, vagina vera squarish in lateral view, female tail subcylindrical with smooth end, and males with 26-30 μm long spicules. The new species was morphologically compared with eight similar species. The molecular phylogenetic relationships of the new species with other relevant species and genera were reconstructed using partial small, large subunit and internal transcribed spacer ribosomal DNA (SSU, LSU D2-D3 and ITS1 rDNA) sequences and the resulting topologies were discussed.