Tehran University of Medical Sciences Journal of Arthropod-Borne Diseases 2322-1984 16 3 2023 02 12 1536 1536 EN Shahyad Azari-Hamidian Professor of Medical Entomology and Vector Control School of Health Research Center of Health and Environment Guilan University of Medical Sciences Seyed-Mohammad Omrani Department of Medical Parasitology, School of Medicine, Shahrekord University of Medical Sciences, Shahrekord, Iran 2022 01 28 2022 12 26 Background: Culex theileri (Diptera: Culicidae) is a known vector of pathogens that cause dirofilariasis, Sindbis fever and West Nile fever in Iran. The species is one of the country’s most abundant and widely distributed species. Methods: In order to conduct a faunistic and bionomic study of mosquitoes, larval collection was carried out in Chahar Mahal and Bakhtiari Province of western Iran using dipping method. Results: In total, some 2096 larvae of Cx. theileri were identified. Among the larvae, 1024 (48.9%) displayed aberra­tions and anomalies in the development of cranial seta 1-C (preclypeal seta). Morphological aberrations and anomalies of seta 1-C in the third- and fourth-instar larvae and abdominal terga of the adults of Cx. theileri collected in Iran are discussed and illustrated. Conclusion: More studies are needed throughout the distribution of Cx. theileri to analyze the variation of the species, especially using both morphological and molecular data. https://jad.tums.ac.ir/index.php/jad/article/view/1536 https://jad.tums.ac.ir/index.php/jad/article/download/1536/599