en Microbiology and Anatomy Microbiology and Anatomy Original Research: Basic Science in Medicine Original Research: Basic Science in Medicine Three media formulated from molasses and cornsteep liquor and another media based on the basal medium formulation of IPS-82 were assessed for the growth and production of insecticidal properties of B. thuringiensis H-14 .• Bacterial powders prepared from the broth cultures were assayed against the larvae of Culex pipiens and Anopheles stephensi. A standard powder of IPS-82 was included in the assay for comparison. Good . growth was obtained in all the media and all powders were effective against the two types of mosquito larvae. Media with the basal medium formulation of Institute Pasteur Paris were the most effective. Molasses III media was also very favorable. The concentrations required to kill 50% of the larvae of Culex pipiens and Anopheles stephensi for these two were as follows: - Media with the basal medium formulation of Institute Pasteur Paris: 24hr. Lc50 and it's 95% confidence limits of Culex pipiens and Anopheles stephensi = 0.0025,0.0031,0.0018 mg/lit 0.1792,0.2603,0.1508 mg/lit - Molasses III Media: 24hr. Lc50 and it's 95% confidence limits of Culex pipiens and Anopheles stephensi = 0.0103,0.0115,0.0092 mg/lit 0.1994,0.2223,0.1769 mg/lit The investigation shows that these media can be used for the production of B.thuringiensis H-14 primary powder. 229 236 http://mjiri.iums.ac.ir/browse.php?a_code=A-10-1-498&slc_lang=en&sid=1 F FAYAZ 20031947532846005597 20031947532846005597 Yes Iranian Research Organization For Science and Technology N MOASAMI 20031947532846005598 20031947532846005598 No School of Public Health and Institute of Public Health Research, M ZAIEM 20031947532846005599 20031947532846005599 No M MOTABAR 20031947532846005600 20031947532846005600 No From the Microbiology Department, Faculty of Medicine, Shahid Beheshti University of Medical Sciences K HOLAKOUEI NAEINY 20031947532846005601 20031947532846005601 No and the Departments of Entomology and Epidemiology, Tehran University of Medical Sciences, Tehran,lslamic Republic of Iran.