Larvae of the secondary screwworm, Cochliomyia macellaria (F.), feed on carrion and may sometimes cause animal myiasis. They have been reared in the laboratory on various animal tissues to study their growth and development because of their importance in forensic science. We use secondary screwworms in our laboratory for preliminary experiments as a model for the primary screwworm, Cochliomyia hominivorax (Coquerel), which has been eradicated from the United States. C. macellaria larvae reared on animal tissues produced a putrid odor, an unfavorable condition in the laboratory, and variable pupal size and weight, bringing into question the validity of use as a model for C. hominivorax. Therefore, studies were conducted to develop a less odiferous artificial diet with reduced variability in resulting pupae by comparing three diets: 1) an artificial diet prepared from spray-dried blood, spray-dried poultry egg, dry milk substitute, and solidified with a polyacrylate polymer gel; 2) a fresh blood-based diet prepared similarly, except fresh bovine blood was used in place of spray-dried blood; and 3) a beef liver diet. Data from seven life-history parameters of resulting insects were collected and analyzed. Larval and pupal weights of C. macellaria reared on both the dry and fresh blood-based diets were significantly higher than those reared on the liver diet. Numbers of pupae and percentage of adult emergence were also significantly higher from both dry blood and fresh blood-based diets than those reared on the liver diet. Female flies developing from larvae reared on dry and fresh blood-based diets laid significantly more eggs than females developing from larvae reared on the liver diet. Results show that C. macellaria larvae developed and grew normally in the dry and fresh blood-based diets, indicating that an artificial diet can effectively replace the liver diet commonly used for rearing C. macellaria.